Consolidated Laser
Ranging Data Format (CRD)
Version
1.01
R. L. Ricklefs
The University of Texas at Austin / Center for Space Research
C. J. Moore
EOS Space Systems Pty. Ltd.
For the ILRS Data Formats and Procedures Working Group
27 October 2009
Revision
History
0.
Revision Summary
l v 0.25 12 February 2007 - Initial public release
l v 0.26 12 March 2007 - Update based on community input
l v 0.27 15 November 2007 - Further updates based on community input
0.1 0.25 12
February 2007
l First public release
0.2 0.26 12 March 2007
l Added sample files
l Added Common
Abbreviations and Resources sections
0.3 0.27 15 November 2007
l Added revision history.
l Added target type to target
header H3.
l Added data quality alert to
station header H4.
l Refined clock offset fields
in the transponder configuration record C4.
l Added "stop
number" to ranging record (10).
l Added origin of values to
meteorological record (20).
l Clarified use of terms
time-of-flight and range.
l Revised station file naming
conventions in Section 5.
l Other changes for
consistency or improved readability.
0.4 1.00 27 June 2008
l Clarify handling of
free-format character fields
l Clarify handling of H4
record unknown stop time.
l Explicitly state that C1
record pulse length is fwhm.
l The units of epoch delay
correction in record C3 have changed to microseconds.
l Record 21 Sky Clarity
suggested format has changed from integer to floating.
l Add detector channel to
'40' calibration record and '11' normal point record.
l Expand data type in '40'
calibration record to handle 1 and 2 way calibrations.
l Add more sample data sets,
including all possible records.
l Add table showing which
records correspond with which data types.
l Note that 3.0 has already
been subtracted from kurtosis.
l Explain 'full rate, fire
only' files (.frf) for one-way transponders.
l Explain possibility of
using '30' pointing angles as fundamental measurements (3.6.2).
l Converted old section 7 and
8 to appendices A and B and inserted sections 7-9.
l Change normal point window
length (record '11') from integer to floating point.
0.5 1.01 27 October 2009
l Various clarifications and
cleanup of wording.
l Reflect changes from Errata
page.
l Changes in handling new
Station Epoch Time Scale values.
l Add reference to EDC
on-line format compliance checking.
Abstract
Due to recent technology
changes, the existing International Laser Ranging Service (ILRS) formats for
exchange of the 3 laser ranging data types full rate, sampled engineering and
normal point - are in need of revision. The main technology drivers are the
increased use of kilohertz firing-rate lasers which make the full rate data
format cumbersome, and anticipated transponder missions, especially the Lunar
Reconnaissance Orbiter (LRO), for which various field sizes are either too
small or non-existent. Rather than patching the existing format, a new flexible
format encompassing the 3 data types and anticipated target types has been
created. This change in formats provides the opportunity to include fields and
features that were desired but not available in the old formats.
Introduction
The purpose of the
Consolidated Laser Ranging Data Format (CRD) is to provide a flexible,
extensible format for the ILRS full rate, sampled engineering, and normal point
data. The primary motivations for
creating a new format at this time is to allow for transponder data, and
to handle high-repetition-rate laser data without unnecessary redundancy. This
format is based on the same features found in the ILRS Consolidated Prediction
Format (CPF), including separate header and data record types assembled in a
building block fashion as required for a particular target.
There are 3 separate
sections to the data format: 1) the header section which contains data on the
such topics as station, target, and start time; 2) the configuration section
containing an expanded version of data previously described by the System
Configuration Indicator (SCI) and system CHange Indicator (SCH) fields; and 3)
the data section containing laser transmit and receive times, and other highly
dynamic information. The data headers are fixed format and similar in content
to those of the CPF files. The configuration and data records are free format
with spaces between entries. Records can be added as needed for the specific
data types and at frequencies commensurate with the data rate. For example, at
a 2 kHz ranging rate, meteorological data and pointing angles are commonly read
far less frequently than the ranges. Note that 1 way out-bound, 1 way in-bound,
and 2 way ranges could all appear within one file. Also note that multiple
colors could appear in one file.
Advantages of this format
over the current ILRS formats are as follows;
Flexibility. The data files
can be simple and compact for kiloHertz ranging or comprehensive for more
complex data structures, as appropriate.
The building block
structure with multiple record type allows for including and omitting certain
records types as needed by a station or target.
Configuration descriptions
are addressed in a more explicit, logical and extensible manner than the current
format.
A single integrated format
can be used for current and future data and target types.
Multiple color data,
multiple ranging modes (transponder one- and two-way ranges) and multiple
configurations can be included naturally within a single data file.
The format can be expanded
in the future as needs expand without abandoning the entire format.
All data types (full rate,
sampled engineering, and normal point) can be managed in a single file if
desired, e.g., for archival and reference purposes.
Extensibility to the
eXtensible Markup Language (XML) is provided for in the design.
Fields in the Configuration
sections are compatible with the SLR Engineering Data File (EDF) format.
There
will often be cases where the value of a data record field is either unknown or
not applicable. This is especially true when data is converted from an old
format to the CRD format, since there will be fields (such as skew and
kurtosis) that do not exist in the old format. In these cases, unless noted
otherwise, numerical fields in the new format should be set to -1 to
indicated no information. Character fields without information should be
filled with na for Not_Available.
In
the following pages, sections 1 3 provide a description and discussion of the
specific file sections and record types. Following that, section 4 gives
examples of the file structure for various types of data. Section 5 addresses
file naming conventions. Section 6 provides some real-world examples of the new
format, while section 7 provides information about implementing and testing the
CRD format on site. Section 8 was included to provide a quick overview of the
new data fields and their use. Appendix A provides web references to formats
and official lists as well as links to CRD test data sets and sample code
containing format converters and CRD file check programs. Finally, Appendix B
provides definitions of abbreviations.
Fields in header records are defined according to the following FIXED
FORMAT specifications (in contrast to data records which will have free
format fields that are delimited by white space). Upper and lower case
characters are both acceptable: e.g., H1 or h1; CRD or crd in H1.
White spaces are allowed (where appropriate) in header record fields since
these are fixed format.
The format header describes information relating to the file: e.g. the
version of the format used, time of production etc.
1-2 A2 Record Type (= "H1" or h1)
4-6 A3 "CRD" or crd (Consolidated Ranging Data format)
8-9 I2 Format Version (currently = 1)
11-14 I4 Year of file production
16-17 I2 Month of file production
19-20 I2 Day of file production
22-23 I2 Hour of file production (UTC)
There must be one and only one format header record in the file and it
(or a 00 comment record) must be the first record.
Format version will be 1 for version 1.00
1.99, 2 for 2.00-2.99, etc. All changes between n.00 and n.99 must be backward
compatible. This means no new fields will be added between existing fields,
etc. New fields could be added to the end of a record or additional record
types could be added.
The station header describes information relating to the station or site
collecting this laser data.
1-2 A2 Record
Type (= "H2" or h2)
4-13 A10 Station
name from official list (e.g., "MOB7 ", "MLRS ")
15-18 I4 Crustal
Dynamics Project Pad Identifier
20-21 I2 Crustal
Dynamics Project 2-digit system number
23-24 I2 Crustal
Dynamics Project 2-digit occupancy sequence number
26-27 I2 Station
Epoch Time Scale - indicates the time scale reference.
3 = UTC (USNO)
4 = UTC (GPS)
7 = UTC (BIH)
1-2, 5-6, 8-9 =
reserved for compatibility with earlier data using obsolete time scales.
10 and above = UTC
(Station Time Scales)
For station-created files, there must be one and only one station header
record in the file and it must be the second record. Data centers may combine
files.
Currently, values of the Station Epoch Time Scale other than 3, 4, and
7 will not be understood by the SLR data analysts, and data including them will
usually be discarded. Since time scales do evolve, and some experiments require
higher accuracies than are available with the current techniques, it was
necessary to include the possibility of new values (10-99) that did not
conflict with current or obsolete historical values. If you believe there is a
compelling reason to use another value (e.g. 10 or above) you must propose the
new value and explain the reasons to the ILRS Analysis Working Group and the
ILRS Data Formats and Procedures Working Group. If they grant approval, you may
use the new value, and it will be documented in this manual.
The Crustal Dynamics Project Pad, site, and occupancy sequence number
are often combined into the CDDIS SOD found in the official pad and code list
mentioned in the introduction to this document.
The target header describes static information relating to the target,
whether it is a satellite, lunar or spacecraft target.
1-2 A2 Record Type (= "H3 or h3)
4-13 A10 Target name from official list (e.g., "Ajisai",
"GPS35")
15-22 I8 ILRS Satellite Identifier (Based on COSPAR ID)
24-27 I4 SIC (Satellite Identification Code)
29-36 I8 NORAD ID
38-38 I1 Spacecraft Epoch Time Scale (transponders only)
0
= Not used.
1
= UTC
2
= Spacecraft Time Scale
40-40 I1 Target type
1=passive (retro-reflector) artificial
satellite
2=passive (retro-reflector) lunar reflector
3=synchronous
transponder
4=asynchronous
transponder
There must be at least one target header (and
associated child records) in a file but there could possibly be more, e.g. for
accumulating normal point data for many targets over a period (e.g. one day)
for transmission to data centers.
COSPAR ID to ILRS Satellite Identification Algorithm:
COSPAR ID Format: (YYYY-XXXA)
YYYY is the four digit year of when the launch vehicle was put in orbit
XXX is the sequential launch vehicle number for that year
A is the alpha numeric sequence number within a launch
Example: LAGEOS-1 COSPAR ID is 1976-039A
Explanation: LAGEOS-1 launch vehicle was placed in orbit in 1976; was the 39th
launch in that year; and LAGEOS-1 was the first object injected into orbit from
this launch.
ILRS Satellite Identification Format: (YYXXXAA),
based on the COSPAR ID
Where
YY is the two digit year of when the launch vehicle was put in orbit
Where XXX is the sequential launch vehicle number for that year
AA is the numeric sequence number within a launch
Example: LAGEOS-1 ILRS Satellite ID is 7603901
The session/pass header describes information relating to the period
over which the data is collected. For normal satellite targets this is
generally each pass, but could be associated with pass segments. For
geostationary satellites and distant targets, it must be related to time
segments as defined by the station. It will be necessary to specify and hence
enforce that certain parameters or conditions remain constant or static during
a session.
The session header is the place to indicate what type of data records
follow this will enforce data records to be provided in blocks of consistent
data rather than allowing sampled engineering, full rate and normal point
records to be randomly intermingled.
Hence there must be a Session Header preceding each block of data and
there may be more than one Session Header for a given pass or segment if
different types of data follow.
1-2 A2 Record Type (= "H4 or h4)
4-5 I2 Data type
0
= full rate
1
= normal point
2
= sampled engineering
7-10 I4 Starting Year
12-13 I2 Starting Month
15-16 I2 Starting Day
18-19 I2 Starting Hour (UTC)
21-22 I2 Starting Minute (UTC)
24-25 I2 Starting Second (UTC)
27-30 I4 Ending Year (Set
ending date and time fields to -1 if not available.)
32-33 I2 Ending Month
35-36 I2 Ending Day
38-39 I2 Ending Hour (UTC)
41-42 I2 Ending Minute (UTC)
44-45 I2 Ending Second (UTC)
47-48 I2 A flag to indicate the data release:
0:
first release of data
1:
first replacement release of the data,
2:
second replacement release, etc
50-50 I1 Tropospheric refraction correction applied indicator
0
= False (not applied)
1
= True (applied)
52-52 I1 Center of mass correction applied indicator
0
= False (not applied)
1
= True (applied)
54-54 I1 Receive amplitude correction applied indicator
0
= False (not applied)
1
= True (applied)
56-56 I1 Station system delay applied indicator
0
= False (not applied)
1
= True (applied)
58-58 I1 Spacecraft system delay applied (transponders) indicator
0
= False (not applied)
1
= True (applied)
60-60 I1 Range type indicator
0
= No ranges (i.e. transmit time only)
1
= 1 way ranging
2
= 2 way ranging
3
= Receive times only
4 = Mixed (for real-time data recording, and combination of 1- and 2-way
ranging, e.g. T2L2)
Important: If Range type indicator is not set to two-way (2) or mixed (4),
all corrections must be written as one way quantities. Specifically, this
applies to range, calibration, refraction correction, center of mass
correction, as well as all RMS and other statistical fields. With mixed,
separate range data (10), normal point (11), and calibration (40) records will
be needed for one-way and two-way data.
62-62 I1 Data quality
alert indicator
0 = good quality;
nominal/uncompromised data.
1 = suspect quality; Some
concerns that data has been compromised
but is still useful and could be used with caution.
2 = poor or unknown
quality; test, experimental or compromised data
not be to be used for scientific purposes.
Note: Details of any data
degradation can be included in comment (00) records,
For normal point records, stations generating the file must set the Center of Mass and Refraction Applied flags to false and provide data consistent with these flags. The format however allows data to be provided where normal point data have these corrections applied e.g. for special purpose users or for use by data centers themselves.
Note that several of the indicator fields, such as refraction and center of mass correction have the opposite meaning of corresponding Merit II flags. For instance, in the Merit II full rate format, center of mass applied is set to 0 if the correction is applied. Here, the flag is set to 1 if the correction is applied.
The station system delay applied indicator is normally set to true for
normal points.
Ending time may be cumbersome to compute if data is being written
directly into the CRD format in real-time. In this case the ending date and
time fields may be filled with -1.
1-2 A2 Record Type (= "H8" or h8)
Include even if it is immediately followed by end of file footer.
1-2 A2 Record Type (= "H9" or h9)
If an end-of-file footer is missing the implication is that the file has
been truncated and has therefore been corrupted. One response could be to
request a retransmission of the file.
Configuration records will hold static data that represents station
specific configuration information used while collecting the data stored in
this file. All fields must be separated by spaces, and white spaces are not
allowed within record fields. These records are FREE FORMAT (except
that the record ID must be in columns 1-2) and rely on white spaces for
parsing. The field sizes (e.g., I5, F12.5) are suggestions, and should be
sized according to the stations needs.
Character strings can be as short as 1 character and as long as 40
characters. Longer strings should be truncated to 40 character on reading. See
example 6.6.
While detailed configuration records are strongly encouraged and are a
vital part of the CRD format, the minimum requirement is a C0 record
containing the Transmit Wavelength and the System Configuration ID, and the
60 Compatibility Record. The 60 record is not required if records C1-C3 are
included, although it may be useful until the format is fully implemented.
Record C4 is always required for transponder data.
The detail type field in the configuration records allows for future
expansion of the configuration record format. At this time, this field will
always have the value 0.
The system configuration record provides a means for identifying all
significant components of a system in operation during collection of the data
records contained within this file. This record will be an extensible list of
configuration records of components deemed necessary to characterize the system
at any given time during which data records are collected.
A2(1-2) Record Type (= "C0" or c0).
I1 Detail Type (= "0").
F10.3 Transmit Wavelength (nanometers)
A4 System Configuration id (unique
within the file)
A4 Component A configuration id (e.g.
laser configuration id)
A4 Component B configuration id (e.g.
detector configuration id)
A4 Component C configuration id (e.g.
local timing system configuration id)
A4 Component D configuration id (e.g.
transponder configuration id)
Repeat as required.
The use of configuration records replaces the current SCI and SCH (but
not the station site log) files. To access information currently contained in
the SCH file, one should use the date and time as a key and extract the
information from station site log files which should be maintained to provide
such data. The SCI file is totally replaced by the records in the current file.
The Transmit Wavelength represent the wavelength of the laser beam as
transmitted to the atmosphere and is thus common to many of the station
subsystems. Hence it is included explicitly in this record. One advantage of
this is that the association of data records to wavelength used is more direct.
The file must contain at least one Configuration Header. If there are
multiple system configurations used when generating the data records contained
within the file, then there should be multiple system configuration headers in
the file. These should appear after the associated component configuration
records have all been defined.
A standard enumerated list of components for many of the configuration
fields will be maintained at the ILRS web site (http://ilrs.gsfc.nasa.gov).
This will include, for example, available detector, laser, and timer types.
The file should contain at least one Laser Configuration record. If
multiple wavelengths are used or there are significant changes to any of the
other parameters within the data sets in the file, then there must be
appropriate Laser Configuration records for each wavelength or configuration
used.
A2(1-2) Record Type (= "C1" or c1).
I1 Detail Type (= "0").
A4 Laser Configuration ID (unique
within the file)
A10 Laser Type (e.g. Nd-Yag)
F10.2 Primary wavelength (nm)
F10.2 Nominal Fire Rate (Hz)
F10.2 Pulse Energy (mJ): record when this
fields changes by 10%
F6.1 Pulse Width (FWHM in ps): record when
this fields changes by 10%
F5.2 Beam Divergence (arcsec)
I4 Number of pulses in outgoing
semi-train
Note that the primary wavelength is used here, e.g. use 1064 for a
Nd-Yag laser even though only 532 is used.
Most fields are expected to be static for a given laser. Pulse energy
and width should trigger the writing of a new record whenever they change by
10%.
The file should contain at least one Detector Configuration record. If
multiple wavelengths are used or there are significant changes to any of the
other parameters within the data sets in the file, then there must be an
appropriate Detector Configuration record for each wavelength or configuration
used.
A2(1-2) Record Type (= "C2" or c2).
I1 Detail Type (= "0").
A4 Detector Configuration id (unique
within the file)
A10 Detector Type (e.g., SPAD, CSPAD, MCP, APD, GeDiode,
)
F10.3 Applicable wavelength (nm)
F6.2 Quantum efficiency at applicable
wavelength (%).
F5.1 Applied voltage (V)
F5.1 Dark Count (kHz)
A10 Output pulse type (ECL, TTL,
photon-dependent,
)
F5.1 Output pulse width (ps)
F5.2 Spectral Filter (nm)
F5.1 % Transmission of Spectral Filter
F5.1 Spatial Filter (arcsec)
A10 External Signal processing
Most fields are expected to be static for a
given detector. Spatial and spectral filters changes should be recorded when
they change by 10% (for continuously variable filters), or whenever they change
(for discrete filters). The field external signal processing can refer to a
particular technique, algorithm, or software program used.
The file should contain at least one station Timing System Configuration
record. If multiple timing systems are used, then there must be an appropriate
Timing System Configuration record for each system used.
A2(1-2) Record Type (= "C3" or c3).
I1 Detail Type (= "0").
A4 Timing System Configuration id
(unique within the file)
A20 Time Source (e.g.Truetime_XLi, Truetime_XL-SD, Datum_9390, HP_58503A, TAC, ...)
A20 Frequency Source (e.g.
Truetime_OCXO, CS-4000, )
A20 Timer (e.g. MRCS, SR620,
HP5370B, Dassault, Other,
)
A20 Timer Serial Number (for multiple
timers of same model)
F6.1 Epoch delay correction (us).
Most of the fields in this record should
effectively be pointers to items in the Station Log File where associated
static data on each device can be found. The epoch delay correction provides a
measure of the propagation delay between the Time Source output and the point
at which the timing epochs are registered. For example, in some systems, a 1PPS
signal is used to latch second boundaries, However there must be some
correction applied for the transmission delay between the source of the 1PPS
signal and the timer system. The epoch delay correction has been applied to the
data, except in the case of transponders, where there is a choice. See record
"C4" in section 2.5 below. Note the difference in units.
The transponders header describes static information relating to certain
transponders
A2(1-2) Record Type (= "C4" or c4).
I1 Detail Type (= "0").
A4 Transponder Configuration ID (unique
within the file)
F20.3 Estimated Station UTC offset
(nanoseconds)
F11.2 Estimated Station Oscillator Drift
(UTC/station clock) in parts in 1015.
F20.3 Estimated Transponder UTC offset
(nanoseconds)
F11.2 Estimated Transponder Oscillator Drift
(UTC/spacecraft clock) in parts in 1015
F20.12 Transponder Clock Reference Time (seconds,
scaled or unscaled)
I1 Station clock offset and drift
applied indicator
0 = Neither
offset nor drift applied
1 = Only
offset applied
2 = Only
drift applied
3 = Both
offset and drift applied
I1 Spacecraft clock offset and drift
applied indicator
0
= Neither offset nor drift applied
1 = Only
offset applied
2 = Only
drift applied
3
= Both offset and drift applied
I1 Spacecraft time
simplified
0
= False
1
= True
Note that standard sense used in all time and frequency metrology must
be followed, e.g. local station offset is (UTC local station).
A transponder configuration record is required only if the target
contains a transponder or time transfer equipment.
To convert from spacecraft master clock units and timescale,
tUTC= tmaster + (tmaster
to) * 10-15 * Oscillator Drift + UTC offset
where to
is Transponder
Clock Reference Time, the time at
which master clock was calibrated against UTC (somehow), and the UTC offset is
(UTC-master)
at time to.
For the space
craft time simplified mode (used for LRO), to has already been removed from tmaster to allow passing of a much smaller
number. The Transponder
Clock Reference Time field is filled but only used for reference. The equation then becomes
tUTC= tmaster + (tmaster)
* 10-15 * Oscillator
Drift + UTC offset.
The conversion for
the station clock is analogous.
A new record
should be written whenever a field changes value.
Data records contain non-static data and hence they all will contain a
time-stamp field. All fields must
be separated by spaces, and white spaces are not allowed within data
fields. These records are FREE FORMAT (except for record type, which
must be in columns 1-2) and rely on white spaces for parsing. The field
sizes for numerics (e.g., I5, F12.5) are suggestions, and should be sized
according to the target's needs and the station's precision. Character fields
may be as short as 1 character and as long as 40 characters. Longer strings
should be truncated to 40 characters on reading. The exception is that the
comment record (id = 00) contents can be up to 80 characters and can contain
white space. There will be no unused or undefined fields. See example 6.6.
Data records of the same type must be in chronological order. In other
words, all normal point records must be in chronological order; all
meteorological records must be in chronological order, etc. Meteorological
records, for instance, may be either interleaved with the normal point records
or kept together. Times assigned to the calibration (40) and session (50)
records are at the discretion of the station, although if there are multiple
calibration records in a pass, the times should be representative of the time
for which they are applicable.
Seconds of day must, at least for now, be given modulo 86400. In other
words, seconds of day must wrap around to 0 at the end of day. Using the pass
start and stop times from the H4 header, it will be possible to unambiguously
determine the day associated with the seconds of day field. To remove any
ambiguity, the satellite pass must not be longer than 1 day (which could occur
for geostationary satellites).
Several types of data records may need to be interpolated to the time of
the range or normal point record by data users. These are the extended range
information record (12) meteorological records (20 and 21), the pointing
angle record (30) and, although it is mainly present for documentation, the
calibration record (40). Some fields (e.g. precipitation type) cannot be
interpolated, while most can. Since these record types are present only after
one or more of their values has changed significantly, a 2-point linear
interpolation will usually suffice.
The full rate range record contains single-shot measurement data. The
file will contain blocks of one or more range records corresponding to a
consistent data type (full rate, sampled engineering) and system configuration.
A2(1-2) Record Type (= "10")
F18.12 Seconds of day (typically to 100 ns for
SLR/LLR or 1 picosecond for transponder/T2L2). For transponders, station clock
correction may be applied.
F18.12 Time of flight in seconds (none, 1-, or
2-way depending on range type indicator); or (for Epoch Event 5) spacecraft
receive time in units of the spacecraft master clock, or seconds if Spacecraft
offset and drift applied indicator is true. Time of flight may be corrected
for station system delay; receive time may be corrected for spacecraft system
delay and/or clock correction.
A4 System configuration id.
I1 Epoch Event - indicates the time
event reference.
Currently, only 1
and 2 are used for laser ranging data.
0 = Ground
receive time (at System Reference Point - SRP) (2 way)
1 =
Spacecraft bounce time (2 way)
2 = Ground
transmit time (at SRP) (2 way)
3 =
Spacecraft receive time (1 way)
4 =
Spacecraft transmit time (1 way)
5 = Ground
transmit time (at SRP) and spacecraft receive time (1 way)
6 =
Spacecraft transmit time and ground receive time (at SRP) (1 way)
I1 Filter Flag
0=unknown
1=noise
2=data
I1 Detector channel
0 = not
applicable or all
1-4 for
quadrant
1-n for many
channels
I1 Stop number (in multiple-stop
system)
0 = not
applicable or unknown
1-n = stop
number
I5 Receive Amplitude - a positive
linear scale value.
The format allows multiple color data to be included in the same file,
with separate normal point statistics, etc.
As noted above, transmit time only, receive time only, 1-way, and 2-way
ranges etc. can appear in the same file, to accommodate transponders.
Note that station transmit and receive times are nominally with respect
to the system reference point (SRP) which will in many cases be the telescope
invariant point. This requires a knowledge of both the transmit delay and
receive delay, which is critical for transponder ranging. It is less critical
for normal satellite (two-way) ranging since errors in distributing the system
delay to these components will cancel.
The full rate data file should include a swathe of data around the
station-assessed signal. The filter flag is used to record whether the station
processing indicates that a return is signal or noise.
The normal point range record contains accepted measurement data formed
into normal point bins. The file will contain blocks of one or more range
records corresponding to a consistent data type and system configuration.
A2(1-2) Record Type (= "11")
F18.12 Seconds of day (typically to < 100ns for
SLR/LLR or <1 ps for transponders). Station clock corrections should be
applied for all targets.
F18.12 Time of flight in seconds (none, 1-, or
2-way depending on range type indicator); or (for Epoch Event = 5) spacecraft
receive time in units of the spacecraft master clock, or seconds if Spacecraft
offset and drift applied indicator is true. Time of flight should be corrected
for station system delay; receive time may be corrected for spacecraft system
delay and/or clock correction.
A4 System configuration id.
I1 Epoch Event - indicates the time
event reference.
Currently, only 1
and 2 are used for laser ranging data.
0 = Ground
receive time (at SRP) (2 way)
1 =
Spacecraft bounce time (2 way)
2 = Ground
transmit time (at SRP) (2 way)
3 =
Spacecraft receive time (1 way)
4 =
Spacecraft transmit time (1 way)
5 = Ground
transmit time (at SRP) and spacecraft receive time (1 way)
6 =
Spacecraft transmit time and ground receive time (at SRP) (1 way)
f6.1 Normal point window length (seconds)
I6 Number of raw ranges (after editing)
compressed into the normal point.
F9.1 Bin RMS from the mean of raw accepted
time of flight values minus the trend function (ps)
F7.3 Bin skew from the mean of raw accepted
time of flight values minus the trend function.
F7.3 Bin kurtosis from the mean of raw
accepted time of flight values minus the trend function.
F9.1 Bin peak mean value (ps)
F5.1 Return rate (%) for SLR or signal to
noise ratio for LLR.
I1 Detector channel
0 = not
applicable or all
1-4 for
quadrant
1-n for many
channels
Note that station transmit and receive times are nominally with respect
to the system reference point (SRP) which will in many cases be the telescope
invariant point. This requires a knowledge of both the transmit delay and
receive delay, which is critical for transponder ranging. It is less critical
for normal satellite (two-way) ranging since errors in distributing the system
delay to these components will cancel.
If there are too few data points to assess pass rms, skew, or kurtosis,
put -1 in the field. It is left to the stations
discretion, subject to ILRS directives, whether to include normal
points having few data points. Kurtosis calculations should follow the
convention in which 3 is subtracted, so that the kurtosis for a normal distribution
is 0.
Detector channel will normally be '0' even for multi-channel systems.
This field is included for flexibility.
As an example of CRD flexibility, LRO normal points will use F28.12
rather that F18.12 for spacecraft receive time format.
The range supplement range record contains optional range data and will
be interspersed with range data to which it is associated. If this record is
used, then it should be created whenever there is a significant change to one
or more fields.
A2(1-2) Record Type (= "12")
F18.12 Seconds of day.
A4 System configuration id.
F6.1 Tropospheric refraction correction
(picoseconds, 1 way)
F6.4 Target center of mass correction
(meters, 1 way)
F5.2 Neutral density (ND) filter value
F8.4 Time bias applied (seconds)
None.
This data record contains a minimal set of meteorological data. At least one record must appear in the data file.
A2(1-2) Record Type (= "20")
F18.12 Seconds of day (typically to 1 milllisec)
F7.2 Surface pressure (mbar).
F6.2 Surface temperature in degrees Kelvin.
F4.0 Relative humidity at Surface in %
I1 Origin of values
0 = measured values
(written whenever a value changes significantly)
1 = interpolated values
applicable at time (seconds of day) given in this record
Sample meteorological records should only be written when one of the
fields changes significantly. As a minimum, a new record should be written
whenever pressure changes by 0.1mB, the temperature changes by 0.1 K, or when
the humidity changes by 5%. The time
(seconds of day) of an interpolated record should match the time in the
following normal point record.
Since meteorological records may be submitted in blocks and not
interspersed with the normal point or range records, it is recommended that the
meteorological records be accumulated and interpolated to the times needed
(e.g., times of normal points or full rate records).
This data record contains an (optional) supplement set of meteorological data. A file must contain at least one meteorological record and may contain one or more meteorological supplement records.
A2(1-2) Record Type (= "21")
F18.12 Seconds of day (typically to 1 milllisec)
F5.1 Wind speed (m/s)
F5.1 Wind direction (degrees azimuth, north
is zero)
A4 Precipitation type (rain, snow,
fog, fine ...TBD)
I3 Visibility (km)
F4.2 Sky clarity ( ie zenith extinction
coefficient)
I2 Atmospheric seeing (arcsec)
I2 Cloud cover (%)
Meteorological records should only be written when one of the fields
changes significantly. The criteria should be at least 2 times the least
significant bit of the sensor, to prevent noise in the lowest bit from
constantly producing new records.
This record contains telescope or beam director pointing (azimuth and elevation) angles, and is optional for normal point data sets. If it is used, the source and nature of this data must be provided.
A2(1-2) Record Type (= "30")
F18.12 Seconds of day (typically to 1 milllisec)
F8.4 Azimuth in degrees
F8.4 Elevation in degrees
I1 Direction flag
0 = transmit & receive
1 = transmit
2 = receive
I1 Angle origin indicator
0 = unknown
1 = computed
2 = commanded (from predictions)
3 = measured (from encoders)
I1 Refraction corrected
0 = False ( in vacuo angles ie angles if no atmosphere is assumed)
1 = True ( apparent angles with refraction included)
Point angle records should only be written when one of the angles changes
significantly. The meaning of significantly should be defined
by the producers and users of this data.
The pointing angles seem to be seldom used in practice. In most cases
when pointing angles are used in data analysis, it is as a cross check that the
pass and station location have been correctly identified. There may be cases
where pointing angles are used with or without ranging data as a fundamental
data type in precision orbit determination. In these cases, the frequency and
care taken in compiling these angle measurements will be much greater. In this
case, it is also possible that pointing angles records will be needed with
normal points.
The calibration record contains statistics of accepted calibration
measurements. It may be associated with calibrations at the station or target.
The file will contain as many calibration records as required, but there must
be at least one station calibration record in the file at the station level.
Each calibration record is applicable to the subsequent block(s) of range
records. There can also be calibrations records to represent several Types of
data. For a transponder for which all fires must be recorded as well as
returns, there should be type 0 (normal ranging) and 1 (station transmit)
A2(1-2) Record Type (= "40")
F18.12 Seconds of day (typically to < 100ns for
SLR/LLR or <1 ps for transponder ranging). Station clock corrections should
be applied for all targets.
I1 Type of data
0=station combined
transmit and receive calibration (normal slr/llr)
1=station
transmit calibration (e.g., one-way ranging to transponders)
2=station
receive calibration
3=target
combined transmit and receive calibrations
4=target
transmit calibration
5=target
receive calibration
A4 System configuration id
I8 Number of data points recorded (=
-1 if no information)
I8 Number of data points used (= -1 if
no information)
F7.3 One way target distance (meters,
nominal) (= -1 if no information)
F10.1 Calibration System Delay (picoseconds)
F8.1 Calibration Delay Shift - a measure of
calibration stability (picoseconds).
F6.1 Root Mean Square (RMS) of raw system
delay (ps). If pre- and post- pass calibrations are made, use the mean of the
two RMS values, or the RMS of the combined data set.
F7.3 Skew of raw system delay values from
the mean. If pre- and post- pass calibrations are made, use the mean of the two
skew values, or the skew of the combined data set.
F7.3 Kurtosis of raw system delay values
from the mean. If pre- and post- pass calibrations are made, use the mean of
the two kurtosis values, or the kurtosis of the combined data set.
F6.1 System delay peak mean value (ps)
I1 Calibration Type Indicator
0 = Not used
or undefined
1 = Nominal
(from once off assessment)
2 = External
cals
3 = Internal
cals
4 = Burst
cals
5 = Other
I1 Calibration Shift Type Indicator
0
= Not used or undefined
1
= Nominal (from once off assessment)
2
= Pre to Post- Shift
3
= Minimum to maximum
4
= Other
I1 Detector channel
0 = not applicable
or all
1-4 for
quadrant
1-n for many
channels
Nominal calibrations are intended for
generally low accuracy systems that do not have access to high precision system
delay measurements, but rather depend on fairly static and infrequent
assessments of system delay. For example, use nominal calibrations for
engineering data while a station is being developed, or for other special
purposes.
Kurtosis calculations should follow the
convention in which 3 is subtracted, so that the kurtosis for a normal
distribution is 0.
It is expected that one calibration record is
included for a normal point data block, but this record could be used to also
provide single shot measurements or
averaged blocks (normal points) of internal calibrations for example.
The session (pass) statistics record contains averaged statistics
derived from measurements taken during the session (or over the duration of a
pass). The file will contain blocks of one or more range records corresponding
to a consistent format. One session statistics record should be associated with
each of these data blocks.
A2(1-2) Record Type (= "50")
A4 System configuration id.
F6.1 Session RMS from the mean of raw,
accepted time of flight values minus the trend function (ps).
F7.3 Session Skewness from the mean of raw
accepted time of flight values minus the trend function.
F7.3 Session Kurtosis from the mean of raw
accepted time of flight values minus the trend function.
F6.1 Session peak mean value (ps)
I1 Data quality assessment indicator. For SLR and LLR data:
0 = Undefined or no comment.
1 = Clear, easily filtered data, with little or no noise.
2 = Clear data with some noise; filtering is slightly compromised by noise level.
3 = Clear data with a significant amount of noise, or weak data with little noise. Data are certainly present, but filtering is difficult.
4 = Un-clear data; data appear marginally to be present, but are very difficult to separate from noise during filtering. Signal to noise ratio can be less than 1:1.
5 = No
data apparent.
This record is only required in combination with
a number of normal point records. It is optional with full rate or engineering
data records.
Kurtosis calculations should follow the
convention in which 3 is subtracted, so that the kurtosis for a normal
distribution is 0.
This record is provided primarily to allow reformatting of old data from the ILRS normal point and full-rate data to this format, without losing existing data.
A2(1-2) Record Type (= "60").
A4 System configuration id.
I1 System CHange indicator (SCH)
A
flag to increment for every major change to the system (hardware or software).
After the value '9' return to '0', and then continue incrementing. The station
and data centers should keep a log in a standard format of the value used, the
date of the change, and a description of the change.
I1 System Configuration Indicator
(SCI)
A
flag used to indicate alternative modes of operation for a system (e.g., choice
of alternative timers or detectors, or use of a different mode of operation for
high satellites). Each value of the flag indicates a particular configuration,
which is described in a log file held at the station and at the data centers.
If only a single configuration is used then use a fixed value. If a new
configuration is introduced then use the next higher flag value. If value
exceeds '9' then return to '0', overwriting a previous configuration flag (it
is not likely that a station will have 10 current possible configurations).
None.
This record is provided to allow special interest users or groups to add non-standard data records. Other users must be able to ignore such records (if they exist in a file) without any impact. Record types outside this range will be reserved for future standard format use.
A2(1-2) Record Type (= "9X", X = 0
9).
3-80 User defined format
These
records should normally be stripped from the file before being sent to the
operations center.
Comment records are optional, and allow users to insert comments or notes as deemed necessary and appropriate. This especially pertains to any data qualities issues designated in the header H4.
A2(1-2) Record Type (= "00").
A80 Free format ASCII comments (terminated
by an end-of-line character).
To ensure line lengths do not become excessive,
a limit of 80 characters is set. Lines exceeding this limit may be truncated.
Multiple comment lines are encouraged. Comment lines can occur anywhere within
a file.
The records as defined should have the potential for storing a quite
complex mix of data types while maintaining data integrity. The format must
support a consistent, unambiguous data set that can be readily parsed for
currently used and expected data sets, and for data sets that are possible in
the future. The data stored in a CRD file should be capable of being stored in
a normalized database and/or expressed in the XML language. The definitions of
the records have kept this in mind.
It is important that, unless totally unavoidable, data fields are not
repeated as this has the potential for undermining the requirement for
unambiguous and consistent data. It is also efficient in terms of file sizing
and storage.
The following table shows the permissible combination of records by data
type. Normally, files will contain only one data type - full rate, sampled
engineering, or normal point. However, the format does allow combining these
files as separate blocks within a data file. See example 6.5. Another way to do
this for a single pass is to start with a common h1/h2/h3 record set. The first
h4 through h8 block could contain full rate data, for instance. The second h4
through h8 block could contain sampled engineering, and the third such block
could contain the normal points. This is possible because the h4 record
contains the date type for the data following (through h8).
|
Record |
Full Rate |
Sampled Engineering (Rarely used) |
Normal Point |
|
Header Section |
|||
|
H1 - Format |
√ |
√ |
√ |
|
H2 - Station |
√ |
√ |
√ |
|
H3 - Target |
√ |
√ |
√ |
|
H4 -Session (Pass) |
√ |
√ |
√ |
|
H8 - EOS |
√ |
√ |
√ |
|
H9 - EOF |
√ |
√ |
√ |
|
Configuration Section |
|||
|
C0 System Configuration |
√ |
√ |
√ |
|
C1 Laser Configuration |
recommended |
recommended |
recommended |
|
C2 Detector Configuration |
recommended |
recommended |
recommended |
|
C3 Timing Configuration |
recommended |
recommended |
recommended |
|
C4 - Transponder Config |
√ transponders; n/a for other
targets |
√ transponders; n/a for other
targets |
√ transponders; n/a for other
targets |
|
Data Section |
|||
|
10 - Range |
√ |
√ |
not allowed |
|
11 Normal point |
not allowed |
not allowed |
√ |
|
12 Range Supplement |
as available |
as available |
as available |
|
20 - Meteorological |
√ |
√ |
√ |
|
21 Meteorological Supp |
as available |
as available |
as available |
|
30 Pointing angles |
√ |
√ |
n/r (usually) |
|
40 Calibration Statistics |
n/r |
n/r |
√ |
|
50 Session Statistics |
n/r |
n/r |
√ |
|
60 - Compatibility |
√ if no C1-C3; n/r otherwise |
√ if no C1-C3; n/r otherwise |
√ if no C1-C3; n/r otherwise |
|
9x User defined |
Usually not transmitted |
Usually not transmitted |
Usually not transmitted |
|
00 - Comments |
as needed |
as needed |
as needed |
n/a = not applicable or not appropriate
n/r = not required
√ = required
Consider a number of cases. The first is simple case where the station
is performing basic satellite tracking and is creating full rate and normal
point files. In practice, this will probably represent the majority of files
most of the time, at least for the present.
A more complex case where a station is performing two-color ranging and
wants to store both full rate and normal point data in the one file, or when a
site is publishing full rate data from experiments in time transfer using
target transponders.
Two files containing full rate for one target and normal point data for
one period (for example, one day). This is typical for existing normal point
(.qld) and full rate (.fr) files being generated at many stations. (Comment
records are not considered here.) As can be seen from the sample data in
section 6, there can be some legitimate variations in record sequence.
Full rate file for 1
target, single system configuration.
Format Header
Station Header
Target Header
Laser Configuration Record
Detector Configuration Record
Timing System Configuration Record
System Configuration Record
Calibration Record
Session Header
Calibration
Record (if required)
Pointing Record /
Mets Record
Data Record
(Full rate) (repeated)
Calibration
Record / Pointing Record / Mets Record (as required)
Data Record
(Full rate) (repeated)
Calibration
Record (if required)
Pointing Record /
Mets Record
End Of Session Header
Session Header
Calibration
Record (if required)
Pointing Record /
Mets Record
Data Record
(Full rate) (repeated)
Calibration
Record / Pointing Record / Mets Record (as required)
Data Record
(Full rate) (repeated)
Calibration
Record (if required)
Pointing Record /
Mets Record
End of session Header
(as many session as
required)
End of file header
Normal point file
for many targets, single system configuration.
Format Header
Station Header
Laser Configuration Record
Detector Configuration Record
Timing System Configuration Record
System Configuration Record
Calibration Record
Target Header
Session Header
Calibration
Record (if required)
Mets Record
Data record (normal
point) ( repeated )
Mets Record
Data record (normal
point) ( repeated )
Mets Record
Pass Record
End of session header
.. other sessions for
this target as required
Target Header
. Repeat as above for
as many targets as required
End of session header
End of file header
This would correspond to files having a record sequence such as
H1 H2 C0 C1 C2 C3 40 H3 H4
20 30 40 10 10 10...20 10 10...30 10 10...40...10 10 20 H8 H4 20 30 40 10 10
10...20 10 10...30 10 10...40...10 10 20 H8 H4...H8...H9
and
H1 H2 C0 C1 C2 C3 40 H3 H4
40 20 11 11 11...20 11 11...20.12 H8 H4 40 20 11 11 11...20 12 H8 H3 H4 40 20
11 11 11...20 11 11...20 12 H8 H4 40 20 11 11 11...20 12 H8...H8...H9
One file containing full rate and normal point data for one target for
one period (for example, one day) from a station performing two-color ranging
(or any other dual configuration ) ranging.
Full rate and normal
point file for 1 target, two system configurations.
Format Header
Station Header
Target Header
Laser Configuration L1 Record
Laser Configuration L2 Record
Detector Configuration D1 Record
Detector Configuration D2 Record
Timing System Configuration (TS) Record
System Configuration S1 Record (L1-D1-TS)
System Configuration S2 Record (L2-D2-TS), or whatever is appropriate
Calibration (system S1) Record C1
Calibration (system S2) Record C2, or whatever is appropriate.
Session Header (full
rate)
Calibration
Records C1 and/pr C2 (if required)
Pointing Record /
Mets Record
Data Record
for S1 (Full rate) (repeated)
Data Record
for S2 (Full rate) (repeated)
Calibration
Records / Pointing Record / Mets Record (as required)
Data
Records for S1 (Full rate) (repeated)
Data
Records for S2 (Full rate) (repeated)
Calibration
Records (if required)
Pointing Record /
Mets Record
End of session Header
Session
Header (normal point)
Mets Record
Data Record for S1
and/or S2(normal point) (repeated)
Mets Record
Data Record for S1
and/or S2 (normal point) (repeated)
Mets Record
End
of session Header
Session Header (full
rate)
. (Repeat
as above for as many sessions as required)
End of session Header
End of file header
This would correspond to files having a record sequence such as
H1 H2 H3 C0 C0 C1 C1 C2 C2
C3 H4 20 30 40 40 10 10 10 10...20 10 10
10 10...30 10 10 10 10...40...10 10 20 H8
H4 20 11 11 11 11...20 11 11 11
11...11 11 11 11...11 11 20 H8 H4 20 30 40 40 10 10 10 10...20 10 10 10 10...30 10 10 10
10...40...10 10 20 H8 H4 20 11 11 11 11...20 11 11 11 11...11 11 11 11...11 11
20 H8
H8 H9.
One file containing full rate data for one target from a station
performing experiments in time transfer via a transponder in association with
another station.
Full rate 1 target,
two system configurations.
Format Header
Station Header
Target Header
Laser Configuration Record
Detector Configuration Record
Timing System Configuration Record
Transponder Configuration Record
System Configuration Record
Calibration Record (Site)
Calibration Record (Target)
Session Header (full
rate)
Calibration
Record (Site) (if required)
Calibration
Record (Target) (if required)
Pointing Record /
Mets Record
Data Record
(Full rate, time of flight and transmit epoch) (repeated)
Data Record
(Full rate, receive epoch only) (repeated)
Pointing Record /
Mets Record
End of session Header
End of file header
In this case, several full rate or normal point sessions from one station are sent in a single file from the station to a data center. There are two ways of doing this:
H1 H2 H3 H4 ... H8
H3 H4 ... H8
...
H3 H4 ... H8 H9
This ordering is more hierarchical and is more compatible with parsing into XML.
H1 H2 H3 H4 ... H8
H1 H2 H3 H4 ... H8
...
H1 H2 H3 H4 ... H8 H9
This ordering is syntactically correct, and may be easier to implement when converting data in the old format to CRD.
Since the proposed data format is so flexible and a file could contain
many data types and cover any period of time, file naming becomes a real issue.
Therefore the following conventions that have been adopted.
1. File names and file
naming conventions do not form the basis for file processing except for files
that have well defined and specific file extensions (such as .Z for extraction
purposes). File processing will require files to be opened and parsed to determine
what operations, if any, are to be performed.
2. File names ending in
.npt, .frd, or .qlk contain single data types, but possibly multiple
satellites and stations.
3. File names ending in
.crd may contain multiple data types.
4. File names ending in
.frf contain all the laser fire times and do not contain valid times of
flight or receive times. This is for one-way transponder missions such as LRO.
5. Files are delivered
to specific file repositories in which it has been agreed and understood that
certain file operations will be performed. Hence the onus is on the supplier to
provide the appropriate type of file to the repository.
6. Published files will
always have a unique file name. (Pertains to station naming conventions.)
7. Release versions are
maintained within the data file headers for every pass or session. Station file
names will echo this release number (if it is consistent within the file), but
data center file names will not - those files will always contain the latest
data release.
This naming convention is for use with files transmitted from the station to the operations centers (unless there is a prior agreement for another protocol).
5.1.1 Single Pass and Data Type
5.1.1.1 Ftp or Scp
File names for ftp or scp transfer should be
ssss_satname_crd_yyyymmdd_hh[mm]_rr.typ
where
ssss is the CDP Pad Identifier (station number)
satname is from a standard ILRS list of spacecraft (lower case)
yyyymmdd is the start date of pass (UTC)
hh is the hour when the pass or pass
segment begins (UTC time scale)
mm is the minute when the pass or
pass segment begins (optional)
rr is the release number (initial release =
"00")
typ is the data type:
frd full-rate data,
qlk sampled engineering ("quicklook") data,
npt normal point data,
crd mixed or unspecified file contents, or
frf full-rate data with
fire times only.
Geostationary satellite
"passes" could be submitted in several files, depending on the
tracking schedules. Files may contain the .Z, .z, .gz, or .zip
extension indicating a particular type of file compression.
5.1.1.2 E-mail Transmission
For e-mail submission this filename should be part of
the Subject field
Subject: npt data ssss_satellite_crd_yyyymmdd_hh_rr
5.1.2 Several Passes or
Data Types
To submit several normal
point, sampled engineering, full rate files or a combination of files at once,
there are 2 recommended procedures. Note that these procedures can be used for
ftp/scp transfers, not email.
5.1.2.1 Combined File
Send a single combined ASCII file. The description of a combined file
name is:
ssss_[satname_]crd_yyyy[mm[dd[_hh]]]_rr.typ
where the fields are the same
as above, and the brackets [] enclose fields that can be omitted depending on
the file contents. Note that the station is always included, since the file
comes from a single station. A split program (available in the sample code)
will be requiredat the operations center
break this file into its component files.
Examples:
7080_crd_20071012_14_00.npt
- normal points for
several passes from different satellites, starting at a particular hour
7080_lageos1_crd_200206_99.crd - lageos-1 data for a month,
with mixed releases
7080_crd_2003_99.frd - full rate
data for a year, with mixed releases.
Notes:
1) This can cover mass resubmissions of
data with a single (new) revision level.
2) Where there are more than
one revision level in a file, the
release
number should be "99".
3) In the case where several
data types are mixed in a file, the typ
could
be "crd".
5.1.2.2 Tar or Zipped File
'Zip' or tar together
several files into a larger file having an appropriate
name:
ssss_crd_yyyy[mm[dd[_hh[mm]]]]_rr.com,
where
satname
has been omitted,
mm
is minute, which has been added to permit more than one transmission an hour,
and
com
is the compression program extension:
zip,
or
tgz.
Examples:
7080_crd_2005_01.zip - an update to some 2005
data files
7090_crd_20071012_1500_00.tgz - a typical hourly transfer
Data centers (e.g. CDDIS and EDC) will use these file names at their ftp and web sites. These are the file names the users will see when retrieving data for their analysis work. Each file will contain only one type of data.
satname_yyyymmddhh.typ
(hourly)
satname_yyyymmdd.typ
(daily)
satname_yyyymm.typ
(monthly)
satname_yyyy.typ
where
- satname is from a standard ILRS list of
spacecrafts;
- yyyy is the 4-digit year,
- mm is the 2-digit month,
- dd is the 2-digit day,
- hh is the 2-digit hour, and
- typ is
frd full-rate
data,
qlk
engineering sampled engineering data,
npt
normal point data.
Examples: starlette_2006091011.frd
lro_200810.npt
Files may contain the .Z or .z extension
indicating file compression.
This section includes passes and samples of passes represented in the
CRD format. Note that record lengths were kept short by using %.xf c
language formats for most floating point fields.
Filename: 7080_ lageos2_crd_20061113_15_00.frd
H1
CRD 1 2007 3 20 14
H2
MLRS 7080 24 19 4
H3
LAGEOS2 9207002 5986 22195 0 1
H4 0 2006 11 13 15 23 52 2006 11 13 15 45
35 1 1 1 1 0 0 2 0
C0 0
532.000 std1
60
std1 5 2
10
55432.0414338 0.047960587856 std1 2 0
0 0 0
12
55432.0414338 std1 20735.0 1601.0000 0.00 0.0000
20 55432.0414338 801.80
28.21 39 0
30
55432.0414338 297.2990 38.6340 0 2 1
40
55432.0414338 0 std1 -1 -1 0.000 -913.0 0.0 56.0 -1.000 -1.000
-1.0 3 3 0
10
55435.6429746 0.047926839980 std1 2 0
0 0 0
12
55435.6429746 std1 20697.0 1601.0000 0.00 0.0000
30
55435.6429746 297.4480 38.7190 0 2 1
...
10
56735.8021609 0.046094881873 std1 2 0
0 0 0
12
56735.8021609 std1 18092.0 1601.0000 0.00 0.0000
30
56735.8021609 15.2330 45.7100 0 2 1
H8
H9
File name: 7080_lageos2_crd_20061113_15_00.npt
H1 CRD 1
2007 3 20 14
H2 MLRS
7080 24 19 4
H3 LAGEOS2
9207002 5986 22195 0 1
H4 1 2006 11 13
15 25 4 2006 11 13 15 44 40 0 0 0 0 1 0 2 0
C0 0
532.000 std1
60
std1 5 2
11
55504.9728030 0.047379676080 std1 2
120 18 94.0 -1.000 -1.000 -1.0 0.0 0
20
55504.9728030 801.80 282.10 39 1
40
55504.9728030 0 std1 -1 -1 0.000 -913.0 0.0 56.0 -1.000 -1.000
-1.0 3 3 0
11
55988.9809589 0.044893190432 std1 2
120 19 83.0 -1.000 -1.000 -1.0 0.0 0
20
55988.9809589 801.50 282.80 39 1
11
56141.8467215 0.044635017248 std1 2
120 28 66.0 -1.000 -1.000 -1.0 0.0 0
11
56223.2817254 0.044605221903 std1 2
120 25 87.0 -1.000 -1.000 -1.0 0.0 0
20
56223.2817254 801.50 282.60 39 1
11
56373.5463612 0.044746486398 std1 2
120 25 78.0 -1.000 -1.000 -1.0 0.0 0
20
56373.5463612 801.50 282.10 39 1
11
56439.9749454 0.044889147842 std1 2
120 25 99.0 -1.000 -1.000 -1.0 0.0 0
11
56565.2288146 0.045288773098 std1 2
120 25 92.0 -1.000 -1.000 -1.0 0.0 0
11
56680.8785419 0.045804632570 std1 2
120 10 55.0 -1.000 -1.000 -1.0 0.0 0
20
56680.8785419 801.50 282.00 39 1
50
std1 86.0 -1.000 -1.000 -1.0 0
H8
H9
File name: 7080_lageos2_crd_20061113_15_00.qlk
H1
CRD 1 2007 3 20 14
H2
MLRS 7080 24 19 4
H3
LAGEOS2 9207002 5986 22195 0 1
H4 2 2006 11 13 15 24 17 2006 11 13 15 44
59 0 0 0 0 0 0 2 0
C0 0
532.000 std1
60
std1 5 2
10
55457.0521861 0.047753624332 std1 2 0
0 0 0
20
55457.0521861 801.80 282.10 39 0
30
55457.0521861 298.3470 39.2230 0 0 0
10
55482.4631214 0.047552685849 std1 2 0
0 0 0
30
55482.4631214 299.4370 39.8100 0 0 0
...
10
56589.0390552 0.045383653062 std1 2 0
0 0 0
20
56589.0390552 801.50 282.00 39 0
30
56589.0390552 6.7380 47.9120 0 0 0
10
56623.4538362 0.045531247776 std1 2 0
0 0 0
30
56623.4538362 8.8120 47.4510 0 0 0
10
56657.6685552 0.045690091816 std1 2 0
0 0 0
30
56657.6685552 10.8230 46.9570 0 0 0
10
56699.7866762 0.045901952309 std1 2 0
0 0 0
30
56699.7866762 13.2310 46.3060 0 0 0
50
std1 86.0 -1.000 -1.000 -1.0 0
H8
H9
File Name: 7810_lageos1_crd_20061230_07_00.npt
H1
CRD 1 2007 3 20 14
H2
ZIMMERWALD 7810 68 1 7
H3
LAGEOS1 7603901 1155 8820 0 1
H4 1 2006 12 30
7 35 34 2006 12 30 8 12 29 0 0 0 0 1 0 2 0
C0 0
846.000 std1
C0 0
423.000 std2
60
std1 9 0
60
std2 9 1
11
27334.1080890 0.051571851861 std1 2
120 36 154.0 -1.000 -1.000 -1.0 0.0 0
20
27334.1080890 923.30 275.40 43 1
40
27334.1080890 0 std1 -1 -1 0.000 113069.0 0.0 138.0 -1.000
-1.000 -1.0 2 2 0
11
27343.5080895 0.051405458691 std2 2
120 28 79.0 -1.000 -1.000 -1.0 0.0 0
11
27372.6080888 0.050895050517 std2 2
120 30 76.0 -1.000 -1.000 -1.0 0.0 0
11
27373.1080893 0.050886342010 std1 2
120 17 158.0 -1.000 -1.000 -1.0 0.0 0
11
28003.8080894 0.042252027043 std1 2
120 19 170.0 -1.000 -1.000 -1.0 0.0 0
20
28003.8080894 923.40 275.50 42 1
11
28008.7080899 0.042208378233 std2 2
120 85 71.0 -1.000 -1.000 -1.0 0.0 0
11
28402.1080897 0.040251470202 std1 2
120 6 183.0 -1.000 -1.000 -1.0 0.0 0
11
28406.5080897 0.040247878310 std2 2
120 45 78.0 -1.000 -1.000 -1.0 0.0 0
11
28620.0080896 0.040574433849 std1 2
120 18 163.0 -1.000 -1.000 -1.0 0.0 0
20
28620.0080896 923.50 275.50 42 1
11
28627.6080899 0.040603966534 std2 2
120 114 71.0 -1.000 -1.000 -1.0 0.0 0
11
29151.2080895 0.045287136931 std2 2
120 7 65.0 -1.000 -1.000 -1.0 0.0 0
11
29156.7080892 0.045360524908 std1 2
120 7 134.0 -1.000 -1.000 -1.0 0.0 0
20
29156.7080892 923.50 275.80 42 1
11
29225.6080889 0.046314735294 std1 2
120 45 164.0 -1.000 -1.000 -1.0 0.0 0
11
29237.7080892 0.046488750878 std2 2
120 50 78.0 -1.000 -1.000 -1.0 0.0 0
11
29326.8080894 0.047825380133 std1 2
120 49 152.0 -1.000 -1.000 -1.0 0.0 0
11
29334.2080895 0.047940570614 std2 2
120 73 85.0 -1.000 -1.000 -1.0 0.0 0
11
29461.4080892 0.050011219353 std2 2
120 29 76.0 -1.000 -1.000 -1.0 0.0 0
11
29477.2080896 0.050279566397 std1 2
120 25 187.0 -1.000 -1.000 -1.0 0.0 0
11
29544.4080897 0.051445695153 std1 2
120 19 164.0 -1.000 -1.000 -1.0 0.0 0
11
29549.5080897 0.051535764981 std2 2
120 14 87.0 -1.000 -1.000 -1.0 0.0 0
50
std1 165.0 -1.000 -1.000 -1.0 0
50
std2 78.0 -1.000 -1.000 -1.0 0
H8
H9
00 This is a recent MLRS
normal point file.
00 Plausible '21' records
have been added
00 Part of the full rate
file has been added, so keep reading.
h1 CRD 1 2008 3 25 1
h2 MDOL 7080 24 19 4
h3 jason1 105501 4378 26997 0 1
h4 1 2008 3 25 0
45 17 2008 3 25 0 55
9 0 0 0 0 1 0 2 0
c0 0 532.000 std ml1 mcp mt1
c1 0 ml1 Nd-Yag 1064.00
10.00 100.00 200.0 -1.00 1
c2 0 mcp mcp 532.000 -1.00
3800.0 0.0 unknown -1.0 0.00 -1.0 0.0 none
c3 0 mt1 TAC TAC
MLRS_CMOS_TMRB_TD811 na 445.9
60 std 5 2
40 2716.0000000 0 std 67 58
-1.000 -883.3 0.0 96.4 0.718 -0.126 364.4 3 3 0
20 2716.000
801.73 286.76 35. 0
21 2716.000 3.1 45 none 20
-1 3 10
11 2726.697640514675 0.013737698432 std 2
15 1 72.7
1.494 -0.536 -32.4
0.67 0
11 2804.507921286791 0.011496837034 std 2
15 1 72.7
1.494 -0.536 -32.4
0.67 0
11 2810.908760187949 0.011334723870 std 2
15 16 65.4
1.229 -1.235 -33.5
10.67 0
20 2822.000
801.73 286.56 35. 0
11 2828.611102554046 0.010908518342 std 2
15 1 72.7
1.494 -0.536 -32.4
0.67 0
11 2850.814029348448 0.010424908601 std 2
15 3 116.6
0.649 -2.333 -86.7
2.00 0
11 3104.347543373788 0.010760099652 std 2
15 2 108.7
0.354 -2.750 -73.5
1.33 0
11 3113.248715491056 0.010963708963 std 2
15 11 78.5
1.345 -0.730 -45.8
7.33 0
11 3124.950255557618 0.011244819341 std 2
15 14 65.2
1.635 0.207 4.5
9.33 0
11 3142.652594816107 0.011696747487 std 2
15 12 74.2
1.369 -0.535 -161.6 8.00 0
11 3150.653650787761 0.011910674436 std 2
15 2 123.0
0.354 -2.750 -83.7
1.33 0
20 3151.000
801.73 286.16 35. 0
21 3152.000 2 80 fog 20 -1
3 10
11 3169.356124039857 0.012431881802 std 2
15 1 72.7
1.494 -0.536 -32.4
0.67 0
50 std 72.7
1.494 -0.536 -32.4 0
h8
00 Note that there was no
h9 end of file record after the h8,
00 so this is a different
part of the same file.
00
00 The following is part of
the full-rate file from the same pass.
00 '21' records have been
added to this example.
00 Even though this is not
transponder data, a c4 record has been dummied.
00 The 'mc1' clock field id
for the c4 record was added to the c0 record.
00 The file also contains
91, 92, and 93 records, which are user-defined.
00 Station-defined records
will normally be stripped off by the station before transmittal.
00 Just bypass them as you
do not know the format.
00 The analysts can also
add their own 9x records if they wish.
h1 CRD 1 2008 3 25 1
h2 MDOL 7080 24 19 4
h3 jason1 105501 4378 26997 0 1
h4 0 2008 3 25 0
45 17 2008 3 25 0 55
9 0 0 0 0 1 0 2 0
c0 0 532.000 std ml1 mcp mt1 mc1
c1 0 ml1 Nd-Yag 1064.00
10.00 100.00 200.0 -1.00 1
c2 0 mcp mcp_varamp 532.000
-1.00 3800.0 0.0 unknown -1.0 0.00 -1.0 0.0 none
c3 0 mt1 TAC TAC MLRS_CMOS_TMRB_TD811
na 445.9
c4 0 mc1 0.000 0.00
1234567890123456.789 0.00 0.000000000000 0 0 0
60 std 5 2
91 8
85 2640 -2438728.97
-4909741.31 5429800.07 1474.0965 -5367.5721 -4187.1144 2
20 2716.000 801.73 286.76 35 0
21 2716.000 3.1 45 none 20
-1 3 10
40 2716.0000000 0 std 67 58
-1.000 -883.3 0.0 96.4 0.718 -0.126 364.4 3 3 0
30 2717.996 326.8923
32.9177 0 1 1
12 2717.9964890 std 0.0
0.0000 0.00 0.0000
30 2725.897 326.6035
33.9991 0 1 1
10 2726.697640514675
0.013737698432 std 2 2 0 0 0
30 2734.998 326.2469
35.2830 0 1 1
10 2738.899248614531
0.013359440021 std 2 1 0 0 0
30 2742.799 325.9195
36.4168 0 1 1
30 2752.100 325.4955
37.8239 0 1 1
10 2752.100991800282
0.012962363200 std 2 1 0 0 0
30 2762.002 324.9939
39.3585 0 1 1
...
21 3309.000 2 80 fog 20 -1
3 10
30 3309.224 164.3231
22.4342 0 1 1
10 3309.224609210523
0.016974823000 std 2 1 0 0 0
93 3309.224609210523 std 0.000
16.660 -20.265 0.97511 -0.00099
-2416.305 35267.021
92 3309.000 -0.0003 0.0003
h8
h9
The following data was written by 2 different programs, showing how field spacing and length can differ in the configuration and data sections.
File 1:
h1 CRD 1 2008
5 8 19
h2 MDOL 7080 24 19 4
h3 giovea 505101 7001 28922 0 1
h4 1 2008
5 8 9 40 23 2008
5 8 9 50 45
0 0 0 0 1 0 2 0
c0 0 532.000 std ml1
mcp_with_amp mt1
c1 0 ml1 Nd-Yag 1064.00
10.00 100.00 200.0 -1.00 1
c2 0 mcp_with_amp
mcp_and_avantek_amp 532.000 -1.00 3800.0 0.0 unknown -1.0 0.00 -1.0 0.0 none
c3 0 mt1 TAC TAC MLRS_CMOS_TMRB_TD811
na 439.45
60 std 5 2
40 34823.000 0 std 398 190
-1.000 402.3 0.0 131.1 0.168 -0.130 494.4 3 3 0
20 34823.000 796.55 287.86
24. 0
11 34945.620986680762
0.167738944021 std 2 300 116 193.32 1.821 0.904 -22.8 3.87 0
11 35237.103254500325 0.167288847260
std 2 300 143 173.04 1.601 -0.009 -61.3 4.77 0
11 35422.490473700898
0.167002428581 std 2 300 19 179.75 1.318 -0.974 -259.7 0.63 0
50 std 178.8 1.711 0.451
-128.2 0
h8
h9
File 2:
h1 CRD 1 2008
5 8 19
h2 MDOL 7080 24 19 4
h3 giovea 505101 7001 28922 0 1
h4 1 2008
5 8 9 40 23 2008
5 8 9 50 45
0 0 0 0 1 0 2 0
c0 0 532.000 std ml1 mcp mt1
c1 0 ml1 Nd-Yag 1064.00
10.00 100.00 200.0 -1.00
1
c2 0 mcp mcp 532.000
-1.0 3800.0 0.0 unknown -1.0
0.00 -1.0 0.00 none
c3 0 mt1 TAC TAC
MLRS_CMOS_TMRB_TD811 na 439.4
60 std 5 2
40 34823.000000 0 std 398
190 -1.000 402.3
0.0 131.1 0.168
-0.130 494.4 3 3 0
20 34823.000 796.55 287.86
24. 0
11 34945.620986680762 0.167738944021 std 2 300
116 193.3 1.821
0.904 -22.8 3.87 0
11 35237.103254500325 0.167288847260 std 2 300
143 173.0 1.601
-0.009 -61.3 4.77 0
11 35422.490473700898 0.167002428581 std 2 300
19 179.7 1.318
-0.974 -259.7 0.63 0
50 std 178.8
1.711 0.451 -128.2 0
h8
h9
During data validation, several stations provided data in which meteorological and calibration records were grouped by record type. While not originally anticipated in the format design, it is not precluded, either. This variation in the format highlighted the need to properly interpolate records of a different epoch from the range or normal point records.
H1 CRD 01 2009 5 10 7
H2 HERL 7840 35 01 04
H3 Ajisai 8606101 1500 16908 0 1
H4 1 2009 5 10 5
29 2 2009 5 10 5
34 48 0 0 0 0 1 0 2 0
C0 0 532.080 ES 10hz SPD5
GPS NA
C1 0 10hz Nd-Yag 1064.16
10.00 20.00 100.0 20.00 4
C2 0 SPD5 SPAD5 532.000
20.00 0.0 0.0
+0.7v 0.0 0.15 20.0 0.0 Single_fot
C3 0 GPS Radiocode_GPS_8000 Radiocode_GPS_8000 HxET_=_3x_dassault No_Sn 0.0
20 19560.960 1015.20
277.50 99. 0
20 19923.840 1015.23
277.70 98. 0
20 20096.640 1015.24
277.80 98. 0
20 20459.520 1015.23
278.10 98. 0
40 18014.400 0 ES
-1 -1 122.977
105420.9 0.0 35.4
0.2 2.9 0.0 2 2 0
40 20355.840 0 ES
-1 -1 122.977
105426.9 0.0 35.4
0.1 2.7 0.0 2 2 0
11 19755.5635353
0.015411425559 ES 2 30.0
42 217.0 0.000
0.000 0.0 5.4 0
11 19786.3810075
0.014973907243 ES 2 30.0
56 213.0 0.000
0.000 0.0 7.3 0
11 19813.6766125
0.014664455551 ES 2 30.0
87 213.0 0.000
0.000 0.0 11.3 0
11 19844.4141312
0.014410182562 ES 2 30.0
66 218.0 0.000
0.000 0.0 8.6 0
11 19871.9499495
0.014271511355 ES 2 30.0
70 208.0 0.000
0.000 0.0 9.1 0
11 19903.0875582
0.014219515428 ES 2 30.0 27
248.0 0.000 0.000
0.0 3.5 0
11 19939.9086510
0.014303031023 ES 2 30.0
36 213.0 0.000
0.000 0.0 4.7 0
11 19966.0837316
0.014456622851 ES 2 30.0
48 234.0 0.000
0.000 0.0 6.2 0
11 19993.1391490 0.014694794599 ES 2
30.0 56 208.0
0.000 0.000 0.0
7.3 0
11 20025.6374106
0.015082008815 ES 2 30.0
46 194.0 0.000
0.000 0.0 6.0 0
11 20053.0926792
0.015489205740 ES 2 30.0
59 185.0 0.000
0.000 0.0 7.6 0
11 20080.3882364
0.015960679555 ES 2 30.0
24 189.0 0.000
0.000 0.0 3.1 0
H8
H9
One way (detector not used):
C0 0
532.0 std1 las1 tim1 lro
C1
0 las1 Nd-Yag 1064.0 10.0 100 200 20 1
C3 0 tim1 TAC na MLRS na 0
C4 0
lro 100 5 325 8 12345678 1 0 1
Two way:
C0 0
532.0 std1 slrd las1 tim1 lro
C1
0 las1 Nd-Yag 1064.0 10.0 100 200 20 1
C2 0
slrd MCP 532.0 8 1300 1 TTL 10 1.0 50 10 none
C3 0 tim1 TAC na MLRS na 0
C4 0
lro 100 5 325 8 12345678 1 0 1
Implementation of the CRD format at the ranging station involves several steps,
l Choosing where to make changes in the station software to write the CRD format files (7.1)
l Making the changes (7.2)
l Testing the changes on site (7.2, 7.3)
l Submitting the old and CRD formatted data in parallel for testing (7.3)
l Discontinuing the old formats (7.3)
These issues and more will be addressed below.
There are several approaches that can be taken to implement the CRD format at a laser ranging station. Briefly they are as follows.
1)Record ranging data in the CRD format. Then the CRD
format becomes the native format for the entire data system. This implies a
great deal of work and the best chance to include all the new fields in the
data. The difficulty of modifying and testing real-time ranging software may
make this approach prohibitive. If the acquisition data format already has all
the needed fields and precision for the CRD format, this approach is probably
not necessary.
2)
After ranging, convert the acquisition data files to the CRD format and proceed
with calibration, filtering, normal pointing, and the like, using the CRD
format as the native format. This takes less work than option 1), and insures
that most or all of the new format features are incorporated in a natural way.
As an example, this is the path chosen for MLRS. The reductions software suite
was not written from scratch, but the read and write code in each was replaced
with corresponding CRD routines, and some hitherto separate lunar and satellite
laser ranging programs were consolidated into single programs.
3)
Take old format normal points, full rate, etc. from the filtering and normal
pointing system on site and convert to CRD-formatted file. Programs to convert
old formats to the CRD format already exist in the sample code suite. This is
quick and easy, but fails to take advantage of the new features of the format.
4)
Some stations may use intermediate files or databases during data processing
that already include all the the desired new fields and extended precision. For
these stations, conversion to the CRD format may be as simple as creating a new
back-end formatter that writes data in the CRD format rather than the old
distribution format.
As with the CPF
implementation, there is a suite of sample code that can help in the CRD format
conversion. This software is supplied as is, and there are no guarantees
associated with it. The software has been tested with a limited amount of data,
and there may still be errors and incomplete implementation of
the CRD standards. This software is meant to be a starting place for
those implementing and managing ranging data in the CRD format. Any bug
corrections or software enhancements would be welcomed by the authors.
The
CRD sample software can be broken into several groups.
1)
Code common to many applications
directory: common_c ('c' version)
directory: crd_rw_c
read_crd.c - read and parse CRD records
write_crd.c - write CRD records
getfield.c - read undelimited data fields from a string
2)
Code common to many applications
directory: common_f ('FORTRAN' version)
read_crdf.f - read and parse CRD records
write_crdf.f - write CRD records
3)
CRD file checkers ('c' only).
directory: crd_chk_c
crd_chk.c - check CRD file for errors
crd_cstg_np_cmp compare CRD and
CSTG normal points from a single pass
crd_merit_fr_cmp compare CRD and
MERIT II full rate data from a single pass
4)
Various conversion utilities between CRD and older SLR/LLR formats ('c' only).
directory: crd_conv_slr_c
crd_to_cstg_np.c - CRD normal points to old normal point
format
crd_to_cstg_ql.c - CRD sampled engineering to old
sampled engineering format
crd_to_merit.c - CRD full rate to old full rate
format
cstg_to_crd.c - Old normal point and sampled engineering
to CRD format
merit_to_crd.c - Old full rate to CRD format
read_cstg.c - Read old normal point and sampled engineering
records
read_merit.c - Read old full rate records
write_cstg.c - Write old normal point and sampled engineering
records
write_merit.c - Write old full rate records
5)
Various conversion utilities from old lunar format to CRD ('c' only).
directory: crd_conv_llr_c
cllr_to_crd.c - Old COSPAR lunar to CRD format
read_llr.c - Read old lunar format records
cospar_llr.h - Header file with old lunar format information
6)
Various CRD file split, merge, sort, and miscellaneous routines.
directory: crd_split_c
crd_split.c - Split multi-pass and multi-data-type file
into separate files using station naming
convention
frd_strip.c - Strip out station-dependent (9x) records and
remove some white space from CRD full rate
file
merge_crd_daily.c - merge single pass normal point, quick
look, and
full rate files into single day files.
7)
Various header and include files
directory: include ('c' and FORTRAN versions)
crd.h - Header file with CRD information ('c')
crd.inc - Header file with CRD information (FORTRAN)
cstg.h - Header file with old normal point and
sampled engineering information
merit.h - Header file with old full rate format
information
To
compile this code on a Linux system, just type
./make.sh
on
the command line.
In selected directories there
are scripts to test the program using supplied data. Data files ending in
".ref" are the reference (or "correct") output from the
conversion programs. To run the tests, and automatically compared results, type
./test.sh
in each of these directories.
Any differences between the test and reference data files will be shown.
Differences in dates in H1 records is normal, as this reflects the time of file
creation.
There is also an on-line resource
for testing format compliance, provided by EDC. The URL is http://129.187.165.2/typo3_crd/ . The new
user needs to go to the Register section and fill out the form. When an email
is received confirming registration, the user may go back to this web site and
upload data files for compliance checking.
Once
software has been converted to produce CRD-formatted data files, the CRD files
must be tested for compliance with the CRD format and consistency with the old
format data. Three tools in the sample code suite can help. The first is
crd_chk, which checks the CRD data file (full rate, sampled engineering, or
normal point) for compliance with the format. There will be a report generated
for each file breaking down the header into easily readable lines. The literal
err will show data fields that are out of compliance. Other error messages
will deal with such issues as out-of-sequence records, missing fields in
records, and so forth. A tally of all record types is also provided.
Crd_cstg_np_cmp
compares the CRD normal point against the old-format normal point for the same
pass. Once again, a report is produced showing errors and tallying information
on the pass. Flags that are not consistent between the 2 formats are noted. The
number of extra normal points in each format are listed. Each of the major
common data fields are compared for consistency, and differences are ranked
according to size. The number of passes
with a perfect match are listed first, followed by those that probably
differing due to round-off error. These 2 categories can be presumed to pass.
Entries in the third and following levels need justification, as do differences
in number of normal points. Some such differences may be due to filtering
differences, and some to blunders in the code or data handling.
Crd_merit_fr_cmp
compares the CRD full rate data against the old-format full rate data. It
provides a report similar to that for crd_cstg_np_cmp, above.
When
the station is satisfied that the CRD files it is producing are correct, their
Operations Center should be contacted about submitting old format and CRD
format data in parallel for some period of time.
The
Operations Center will then use software similar to that described above to
validate the data with respect to the CRD format and the old-format data.
Passes that fail the tests will be sent back to the stations for further work.
The goal of this step is to identify and correct (or explain) passes that could
skew the precision orbit determination (pod) solutions.
When
the Operations Center has validated the data to the best of its ability, two
weeks of data will be submitted to various Analysis Centers for validation.
Data for different target types may be sent to different AC's as required. The purpose of this step is to
demonstrate that small differences in the data due to round off and filtering
have no significant consequence to the pod solution.
After
the AC's and OC's have been satisfied, the station will be notified and
production of data files in the old format may cease.
Note: These procedures are
preliminary and may change based upon experience.
While the introduction to this document contains a list of advantages of the CRD over previous formats what follows is a list of advantages the analysts will be most interested in.
1. Skew, Kurtosis, peak-mean are data fields that have been requested over the years but have not been available in the data set. This should allow analysis of over-filtering and anomalous data distributions.
2. The CRD format is capable of handling multi-channel, multi-stop, multi-color systems. Although the old formats could handle multiple color data, they could not be integrated into one normal point file. Multi-channel and multi-stop data is not explicitly recognized in the old formats.
3. Standard satellite, transponder, and lunar data can be fully represented in one format.
4. The free format data records mean the number of significant digits can be increased to the accuracy required by some missions without requiring all targets to carry additional digits.
5. Most station configuration information can now be embedded with the data. This can help with keeping track of station configurations at a finer granularity than the current SCH and SCI values. This will only help if stations use the new configuration section and if values are current. This is an area that many analysts will not be interested in, but the data is readily available for those who are.
6. The all-in-one, building-block nature of the format should make processing full-rate and other special formats easier, if they are needed. Also, full-rate files will be smaller than with the Merit II format.
7. Future enhancements to the format should not require starting over again.
H1 format header
l Date of file production (as distinct from release number in H4) tells when the current file was created (by the station, or the operations center merge or split programs, etc.). This could help verify that the latest file is available.
H2 station header
l The station name may be more recognizable than the pad ID.
H3 target header
l All 3 commonly used satellite IDs are included.
l Spacecraft epoch time scale is available for transponders
l Target type (passive satellite, passive lunar, transponder, mixed, etc.) will allow sending data to the right processing steps for the target
H4 session header
l A flag tells whether this is full rate, normal point or sampled engineering data. This starts a data block for a particular station, satellite, and time span which ends with the next H8 record.
l Provides many of the fields in the Merit II formats but watch the sense of the flags.
l Indicates whether this is 1 or 2 way ranging, etc. needed for processing decisions.
l Data quality alert will give some sense as to whether the data should be used in critical applications.
H8 end of session/pass
H9 end of file
C0 system configuration
l Provides wavelength and pointers to related configuration information for this wavelength.
C1 laser configuration
l Various info including fire rate, pulse width, divergence, number of pulses.
l These could all be of interest in analysis.
l For example, does the pulse width match the rms of the calibrations and data?
C2 detector configuration
l Contains detector information, such as detector type, quantum efficiency, spectral and spatial filters.
l The data biases and corrections may depend on the detector type, e.g. whether the detector is a cspad or mcp.
l Is the change of signal processing algorithm the reason for changes to this station's biases?
C3 timing system configuration
l Is a new station bias correlated with changes to any of these pieces of equipment?
C4 transponder/clock configuration
l This record is needed for transponder analysis where the spacecraft and ground station need to be merged, and both are running on separate clocks.
10 range record
l Variable precision in seconds of day and the return field allow for increased precision for transponders.
l Epoch event will tell how to interpret time of flight/receive time field, and allows for transponder data.
l Detector channel and stop number show where the data comes from. Each channel could have a separate bias.
11 - normal point
l Again, epoch event will tell how to interpret time of flight/receive time field, and allows for transponder data.
l Normal point window length gives the length in seconds, for those targets that require variable normal point lengths (lunar, satellites with highly elliptical orbits).
l Skew, kurtosis and peak-mean can show anomalies in the data distribution that would indicate hardware or processing problems. Since lasers do not produce Gaussian distributions, a skew that is unusually symmetrical could indicate over-filtering.
l Return rate could give some sense of system performance, tempered by sky conditions.
12 - range supplement
l Nothing new except time bias.
20 meteorological record
l Origin of values specifies where the values came from (measured or interpolated value).
21 - meteorological supplement record
l This contains various ancillary data that could correlate with return rate.
40 Calibration record
l Can include target system delays (transponder).
l Number of fires and points used could indicate quality of calibration results.
l Skew, kurtosis, and peak-mean are also included here.
50 Session (pass) statistics record
l Provides skew, kurtosis, and peak-mean for the entire pass.
60 Compatibility record
l Includes old system change indicator (SCH) and system configuration indicator (SCI) for those stations not including c1-c3 configuration records.
9x user defined records
l Not applicable. The analysts will normally not see these.
00 comment record
l If the
station considers data suspect, or if there is anything unusual that is not
covered in the configuration records, this record type can provide an
explanation. These should be kept with the data.
The CRD format offers a number of improvements over the existing, separate normal point, sample engineering, and full rate data formats. Stimulating the development of the new format were the need for extended fire time precision and additional fields for transponder missions such as LRO and the need for reduced size for full rate data from high-repetition-rate laser systems. In order to satisfy these needs, to add functionality not previously seen, and to make provision for additional revisions in the future, the formats were redesigned and combined into a single format. The CRD format has features in common with the Consolidated Predictions Format (CPF) introduced earlier. The files are separated into headers records, data records, and, for the CRD format, configuration records. Each of these 3 sections has some records that are needed only for specific missions types or station capabilities, allowing a great deal of versatility. Care was taken to make the format compatible with the Engineering Data Format (EDF), and was developed with XML in mind.
The format was developed under the auspices of the ILRS Data Formats and Procedures Working Group. The authors would like to recognize the active participation and many contributions of the members of the DF&P WG and the world-wide laser ranging community and the support of NASA and EOS.
The official list of
satellite names and numerical identifiers can be found at:
http://ilrs.gsfc.nasa.gov/products_formats_procedures/satellite_names.html
.
The satellite numerical
identifiers can be found at:
http://ilrs.gsfc.nasa.gov/satellite_missions/list_of_satellites/index.html .
The official list of
station names can be found in the Code column at:
http://ilrs.gsfc.nasa.gov/stations/sitelist/index.html .
The official list of
station monument (pad) numbers and codes can be found at:
http://ilrs.gsfc.nasa.gov/stations/sitelist/index.html .
Find information on site
files at:
http://ilrs.gsfc.nasa.gov/stations/site_procedures/site_logs/site_log_procedure.html .
Find formats for the
pre-CRD data formats at:
http://ilrs.gsfc.nasa.gov/products_formats_procedures/normal_point/np_format.html
and
http://ilrs.gsfc.nasa.gov/products_formats_procedures/fullrate/fr_format_v3.html .
The latest official version
of this document can be found at:
http://ilrs.gsfc.nasa.gov/products_formats_procedures/crd.html .
Test data can be found at:
http://ilrs.gsfc.nasa.gov/products_formats_procedures/crd.html .
CRD Sample Code (format
converters and check programs) can be found at:
http://ilrs.gsfc.nasa.gov/products_formats_procedures/crd.html .
CRD Consolidated laser Ranging Data Format
COSPAR Committee on Space Research, a Committee of ICSU, the International Council for Science.
CPF Consolidated laser ranging Prediction Format
FWHM Full width at Half Maximum, relating to pulse width
ILRS International Laser Ranging Service
LLR Lunar Laser Ranging
LRO Lunar Reconnaissance Orbiter
ND Neutral Density, which describes opacity of a broad band optical filter.
NORAD The North American Aerospace Defense Command
ns nanoseconds
ps picoseconds
RMS Root Mean Square. Same as standard deviation.
SLR Satellite Laser Ranging
SCH Station Change Indicator
SCI Station Configuration Indicator
SIC Satellite Identification Code, a 4 digit satellite descriptor.
SRP System Reference Point, usually described as the first non-moving point in the telescope light path.
us microseconds
UTC Coordinated Universal Time, formerly known as Greenwich Mean Time (GMT).
XML eXtensible Markup Language.