Mars Exploration Rover (MER) Software Interface Specification

Interface Title: APXS Experiment Data Record (EDR) Mission: MER Date: July 30, 2004 Module ID: SIS-SCI008-MER Module Type (REFerence Only or MISsion-specific info included): MIS

Reference Module ID: N/A Date: N/A

Signatures GDS Generating Elements: Ops Product Generation Subsystem (OPGS) Justin Maki ______________________________________________________ Subsystem Engineer Date GDS Receiving Elements: MER GDS SOAS Subsystem Engineer Deborah Bass ______________________________________________________ Subsystem Engineer Date Concurrance: APXS Payload Element Lead Rudolf Rieder ______________________________________________________ PEL Date MER APXS Investigation Scientist Albert Yen ______________________________________________________ Investigation Scientist Date MER Science Manager John Callas ______________________________________________________ Manager Date PDS Central Node Data Engineer Betty Sword ______________________________________________________ Data Manager Date MER MIPL Cognizant Engineer Doug Alexander ______________________________________________________ Cognizant Engineer Date GDS: Ground Data System (GDS) Frank Singleton ______________________________________________________ GDS SE Date

Mars Exploration Rover (MER) Project

APXS EDR Software Interface Specification (SIS)

Version 2.01

Prepared by:

Edward A. Guinness

MER APXS SIS Custodian

Helen Mortensen

Paper copies of this document may not be current and should not be relied on for official purposes. The current version is in the MER Project Library at http://mars03-lib.jpl.nasa.gov, in the Controlled Documents and Records folder.

JPL D-22848

July 30, 2004

Jet Propulsion Laboratory

California Institute of Technology

CHANGE LOG

TBD ITEMS

SECTION

DESCRIPTION

CONTENTS

CHANGE LOG............................................................................................................................... ii

TBD ITEMS................................................................................................................................... iv

CONTENTS................................................................................................................................... v

LIST OF FIGURES....................................................................................................................... vi

LIST OF TABLES........................................................................................................................ vi

ACRONYMS AND ABBREVIATIONS...................................................................................... vii

GLOSSARY.................................................................................................................................. ix

1. INTRODUCTION....................................................................................................................... 1

1.1 Purpose and Scope........................................................................................................... 1

1.2 Contents............................................................................................................................... 1

1.3 Applicable Documents and Constraints........................................................................... 1

1.4 Relationships with Other Interfaces................................................................................... 2

2. Data Product Characteristics and Environment........................................ 2

2.1 Instrument Overview............................................................................................................ 2

2.2 Data Product Overview...................................................................................................... 3

2.3 Data Processing................................................................................................................. 3

2.3.1 Data Processing Level............................................................................................... 3

2.3.2 Data Product Generation............................................................................................ 4

2.3.3 Data Flow..................................................................................................................... 4

2.3.4 Labeling and Identification.......................................................................................... 5

2.4 Standards Used in Generating Data Products................................................................ 7

2.4.1 PDS Standards........................................................................................................... 7

2.4.2 Time Standards........................................................................................................... 7

2.4.3 Coordinate Systems................................................................................................... 7

2.4.4 Data Storage Conventions......................................................................................... 9

2.5 Data Validation................................................................................................................... 9

3. Detailed Data Product Specifications............................................................. 10

3.1 Data Product Structure and Organization...................................................................... 10

3.2 Data Format Descriptions............................................................................................... 10

3.3 Label and Header Descriptions...................................................................................... 14

3.3.1 PDS Label................................................................................................................. 14

3.3.2 PDS Data Objects.................................................................................................... 14

4. Applicable Software.................................................................................................. 15

4.1 Utility Programs................................................................................................................ 15

Appendix A - Example of AN APXS-EDR Label....................................................... 16

APPENDIX B - APXS Label Keyword Definitions................................................... 26

LIST OF FIGURES

Figure 1: S, S_R, and R Frame Coordinate Systems................................................................. 9

Figure 2:The APXS EDR consists of two files....................................................................... 10

Figure 3: Schematic of an APXS EDR data file...................................................................... 11

Figure 4: Data structure for an APXS measurement.............................................................. 11

LIST OF TABLES

Table 1: Product and Software Interfaces to this SIS................................................................ 2

Table 2: Processing Levels for Science Data Sets.................................................................. 3

Table 3: Coordinate Frames Used for MER Surface Operations........................................... 8

Table 4: MER APXS Measurement Data Components......................................................... 12

Table 5: MER APXS Engineering Data Component.............................................................. 13

ACRONYMS AND ABBREVIATIONS

ASCII	American Standard Code for Information Interchange
APSS	Activity Planning and Sequencing Subsystem
APXS	Alpha Particle X-ray Spectrometer
CODMAC	Committee on Data Management and Computation
EDR	Experiment Data Record
FEI	File Exchange Interface
ICD	Interface Control Document
IDD	Instrument Deployment Device
ISO	International Standards Organization
JPL	Jet Propulsion Laboratory
Kbyte	Kilobytes
LSB	Least Significant Byte
MB	Mega Bytes
MER	Mars Exploration Rover
MIPL	Multimission Image Processing Laboratory
MSB	Most Significant Byte
NASA	National Aeronautics and Space Administration
ODL	Object Description Language
OPGS	Operations Product Generation Subsystem
OSS	Operations Storage Server
PDS	Planetary Data System
PEL	Payload Element Lead
PPPCS	Pointing, Positioning, Phasing & Coordinate Systems
RAM	Random Access Memory
RDR	Reduced Data Record
RSVP	Rover Sequence and Visualization Program
SAP	Science Activity Planner
SCM	Spacecraft Configuration Manager
SFDU	Standard Formatted Data Unit
SIS	Software Interface Specification
SOAS	Science Operations Analysis Subsystem
SSW	System Software
TBD	To Be Determined
TC	Temperature Compensation
TDS	Telemetry Delivery Subsystem
URL	Universal Resource Locator
WEB	Warm Electronics Box

GLOSSARY

1. INTRODUCTION

1.1 Purpose and Scope

The purpose of this data product Software Interface Specification (SIS) is to provide users of the Alpha Particle X-ray Spectrometer (APXS) Experiment Data Record (EDR) with a detailed description of the product and a description of how it was generated, including data sources and destinations. An APXS EDR contains data for twelve measurements, each of which consists of an alpha, x-ray, and background spectrum, along with temperature data. The APXS EDR data are stored in binary format. The APXS science team will produce a set of APXS Reduced Data Record (RDR) products in ASCII format. The RDRs will be described in a separate SIS document.

This SIS is intended to provide enough information to enable users to understand the APXS EDR data product. The users for whom this SIS is intended are software developers of the programs used in generating the EDR products and scientists who will analyze the data, including those associated with the Mars Exploration Rover (MER) Project and those in the general planetary science community.

1.2 Contents

This data product SIS describes how the MER APXS instrument acquires its data, and how the data are processed, formatted, labeled, and uniquely identified. The document discusses standards used in generating the product and software that may be used to access the product. The data product structure and organization is described in sufficient detail to enable a user to read the product. Finally, an example of a product label is provided.

1.3 Applicable Documents and Constraints

This data product SIS is responsive to the following MER documents:

1. Mars Exploration Program Data Management Plan, R. E. Arvidson, S. Slavney and S. Nelson, Rev. 3, March 20, 2002.

2. Mars Exploration Rover Project Archive Generation, Validation and Transfer Plan, R. E. Arvidson and S. Slavney, JPL D-19658, March 22, 2002.

3. MER Flight-Mission Systems ICD (FMICD), Vol. 4 Command Dictionary, MER 420-3-15.04, JPL D-20616.

4. MER Flight-Mission Systems ICD (FMICD), Vol. 7 Telemetry Dictionary, MER 420-3-15.047 JPL D-20617.

5. Pointing, Positioning, Phasing & Coordinate Systems Master (PPPCS), S.R. Doudrick, JPL D-19720, June 28, 2001.

This SIS is also consistent with the following Planetary Data System documents:

6. Planetary Data System Data Preparation Workbook, Version 3.1, JPL D-7669, Part 1, February 1, 1995.

7. Planetary Data System Data Standards Reference, Version 3.6, JPL D-7669, Part 2, August 1, 2003.

8. Planetary Science Data Dictionary Document, JPL D-7116, August 28, 2002.

9. Mars Exploration Rover Alpha Particle X-Ray Spectrometer Information Interface Control Document, R. Heninger, Rev. B, JPL-D20251, September 10, 2002.

Finally, this SIS is meant to be consistent with the contract negotiated between the MER Project and the Athena Principal Investigator (PI) in which experiment data records and documentation are explicitly defined as deliverable products.

1.4 Relationships with Other Interfaces

Changes to this APXS EDR SIS document affect the products, software, and/or documents listed in Table 1.

Table 1: Product and Software Interfaces to this SIS

Name	Type P=product S=software D=document	Owner
APXS EDRs	P	OPGS/MIPL
mertelemproc	S	MIPL
MIPL database schema	P	MIPL
APXS RDRs	P	APXS Science Team
APXS RDR SIS	D	APXS Science Team
Other APXS Programs/Products/Documents	P/S/D	APXS Science Team
apxs2asc	S	Geosciences Node

2. Data Product Characteristics and Environment

2.1 Instrument Overview

The MER APXS instrument is similar to the APXS flown on the Mars Pathfinder rover, but without the proton mode. The MER APXS will determine the dominant elements that make up martian surface rocks and soils by irradiating a sample with alpha particles and x-rays from a radioactive source. It will measure the energy spectra of backscattered alpha particles and emitted x-rays. The instrument consists of a sensor head mounted on the rover's Instrument Deployment Device (IDD), and electronics mounted in the rover's Warm Electronics Box. The sensor head contains six radioactive sources and six alpha detectors and one x-ray detector. The instrument also has two temperature sensors; one located on the sensor head and one located on the electronics board. The APXS can measure two separate onboard calibration targets for post-landing calibration.

Most APXS data collection on Mars will be done at night. APXS data are stored in the instrument's RAM, which contains twelve 2.5 Kbyte sections of memory. During a measurement session, data are accumulated and stored in a 2.5 Kbyte working area of memory within the instrument's RAM. After 90 minutes, the measurement is halted and the current measurement data are shifted to the next 2.5 Kbyte section of memory, the working area is cleared, and the measurement is restarted. Thus, the APXS memory can store up to twelve sets of measurements. After twelve measurements are collected, the oldest measurement is discarded as a new 2-hr measurement starts.

2.2 Data Product Overview

Each APXS EDR will consist of two files. The first file is an ASCII formatted detached PDS label. The second file is a binary data file. The APXS EDR data file is a copy of what was in the APXS memory buffer. That is, the EDR consists of unprocessed experiment data stored in binary format. The APXS EDR contains energy spectra in units of counts and temperature values. Temperatures are derived from the two temperature sensors. There are two types of APXS spectra in each measurement: one x-ray, and two alpha spectra. The energy scale is divided into discrete channels with 256 channels for the alpha spectra and 512 channels for the x-ray spectra.

Both alpha spectra use the same detectors, but the second alpha detectors are covered, thus measuring only background events.

The instrument holds data for the twelve most recent measurements in memory. When a new measurement begins, the oldest one is discarded. Each spectrum has a unique identifier. There are also 2 Kbytes at the end of the APXS EDR data file that are transferred from the instrument's internal RAM. This 2 Kbyte section of RAM is used for instrument engineering data.

2.3 Data Processing

2.3.1 Data Processing Level

This SIS uses the Committee On Data Management And Computation (CODMAC) data level numbering system to describe the processing level of the EDR data product. APXS EDR data products are considered CODMAC "Level 2" or "Edited Data" (equivalent to NASA level 0) products. The EDR data files are generated from "Level 1" or "Raw Data", which are the telemetry packets within the project specific Standard Formatted Data Unit (SFDU) record. Refer to Table 2 for a breakdown of the CODMAC and NASA data processing levels.

Table 2: Processing Levels for Science Data Sets

2.3.2 Data Product Generation

The APXS EDR data products will be generated by the MIPL (Multimission Image Processing Laboratory) at JPL under the OPGS using the telemetry processing software, mertelemproc. The EDR data products will be raw uncalibrated data reconstructed from telemetry data products and formatted according to this EDR SIS. Meta-data acquired from the telemetry data headers will be used to populate the PDS label. There will not be multiple versions of an APXS EDR. If telemetry packets are missing during the initial downlink from the rover memory, partial data sets will be created and the missing data will be filled with [zeroes]. The data will be reprocessed after all data are received and the original version will be overwritten.

The APXS memory is maintained by a battery, and in theory, retransmits from the APXS memory could be commanded. In this instance, a new data product will be created, because there will likely be subtle and potentially useful changes in the data when a retransmit from the APXS memory is commanded.

2.3.3 Data Flow

The APXS EDR data products generated by MIPL during operations are created collectively from: a) SSW data products b) SPICE kernels, and c) a meta-data database. They are created on the OSS and then deposited into MIPL's File Exchange Interface (FEI) for electronic distribution to remote via a secure subscription protocol. After a data validation period, the APXS EDR data products are collected with other science data andwritten to physical media for archiving with the Planetary Data System [see reference 2].

The size of the APXS EDR data file is 0.032 MB. The APXS EDR will be generated 60 seconds after the data product for the EDR has been received by MIPL. The APXS data will be reprocessed only if packets in the original downlink are not received. Partial files are created with missing data filled with zeroes. The APXS EDR will be reprocessed after all data is retransmitted and received and the original version will be overwritten and placed into FEI for distribution.

2.3.4 Labeling and Identification

There is a file naming scheme adapted for the MER image and non-image data products. The scheme applies to the EDR and several RDR data products. The file naming scheme adheres to the Level II 27.3 filename convention to be compliant with PDS standards.

Each MER EDR or RDR data product can be uniquely identified by incorporating into the product filename the Rover Mission identifier, the Instrument identifier, the Starting Spacecraft Clock count (SCLK) of the camera event, the data Product Type, the Site location, the rover Position within the site, the Sequence number, the camera "Eye", the spectral Filter, the product Creator identifier and a Version number. For non-camera data, several fields do not apply.

Each APXS EDR has a detached PDS label associated with the APXS binary data file. The file naming scheme for the APXS EDR and RDR data products is formed by:

<rover><inst>< sclk><prod><site>< pos><seq><eye>< filt><who><ver> .<ext>

2.4 Standards Used in Generating Data Products

2.4.1 PDS Standards

The APXS EDR complies with Planetary Data System standards for file formats and labels, as specified in the PDS Standards Reference [7] and the Planetary Science Data Dictionary Document [8].

2.4.2 Time Standards

The PDS label for an APXS EDR uses keywords containing time values, such as start time, stop time, start spacecraft clock count, and stop spacecraft clock count. Each time value standard is defined according to the keyword definition. See Appendix B.

2.4.3 Coordinate Systems

The coordinate systems defined for MER surface operations are listed in Table 3 and illustrated in Figure 1 below. Refer to the Pointing, Positioning, Phasing and Coordinate Systems document [5] for more details. The APXS coordinate system is defined relative to the Rover XYZ coordinate system (ROVER_FRAME).

Table 3: Coordinate Frames Used for MER Surface Operations

Figure 1: S, S_R,and R Frame Coordinate Systems

2.4.4 Data Storage Conventions

The APXS EDR data files contain binary data. Spectral data are 16-bit integers stored in LSB first order. Temperature data are 8-bit integers. The detached PDS labels for APXS EDR's are stored as ASCII text.

2.5 Data Validation

Validation of the MER EDRs will fall into two primary categories: automated and manual. Automated validation will be performed on every EDR product produced for the mission. Manual validation will only be performed on a subset.

Automated validation will be performed as a part of the archiving process, and will be done simultaneously with the archive volume validation. Validations performed, will include such things as verification that the checksum in the label matches a calculated checksum for the data product (i.e., that the data product included in the archive is identical to that produced by the real-time process), a validation of the PDS syntax of the label, a check of the label values against the database and against the index tables included on the archive volume, and checks for internal consistency of the label items. The latter include such things as verifying that the product creation date is later than the earth received time, and comparing the geometry pointing information with the specified target. As problems are discovered and/or new possibilities identified for automated verification, they will be added to the validation procedure.

Manual validation of the data will be performed both as spot-checking of data throughout the life of the mission, and comprehensive validation of a subset of the data (for example, a couple of days' worth of data). These products will be viewed by a human. Validation in this case will include inspection of the image or other data object for errors (like missing lines) not specified in the label parameters, verification that the target shown / apparent geometry matches that specified in the labels, verification that the product is viewable using the specified software tools, and a general check for any problems that might not have been anticipated in the automated validation procedure.

3. Detailed Data Product Specifications

3.1 Data Product Structure and Organization

The structure of the APXS EDR consists of a detached ASCII PDS label and a binary data file as shown in Figure 2.

3.2 Data Format Descriptions

An APXS EDR data file consist of a 32 Kbyte block of APXS binary data with a detached ASCII PDS label (see sec. 3.2.1). Each 32 Kbyte block of APXS data is a copy of the instrument's memory and contains data for twelve measurements. Each measurement consists of APXS spectra and temperature data. The APXS EDR also contains a 2 Kbyte block of engineering data from the instrument's internal RAM (Figure 3).

An APXS measurement counts events for up to 90 minutes. Data remain in APXS memory buffer until 12 new measurements are collected. Thus, an EDR contains data collected for up to 18 hours. Each spectrum is automatically given a unique identifier by the APXS instrument and this identifier is stored with the spectrum.

Each APXS measurement is 2.5 Kbytes long and contains 1024 bytes of x-ray data, two 512 bytes of alpha particle data, and 512 bytes of temperature data (Figure 4). The detailed measurement record structure is shown in Table 4. Alpha particle spectra contain 256 channels and x-ray spectra have 512 channels. Values for all channels are 16-bit binary integers in LSB first order. The first channel (channel 0) of each spectrum contains the time that the instrument was available to count events. This length of time, termed the lifetime, is stored in units of 10 seconds. It gives the time the instrument was able to detect signals. This means, measuring time minus processing time. When a signal is processed, other signals were ignored during the period. The value of lifetime should nominally be 540 (i.e., total lifetime of 5400 seconds or 90 minutes). The twelve least significant bits of the second channel (channel 1) of each spectrum contains a sequential number generated by the instrument to identify the measurement. The value is incremented by one after every cycle start command or internal cycle. Channels 2 and 3 in all but the temperature data are the temperature correction factors that were valid when the spectra were started. Temperature compensation values A0 and G are 16-bit values, MSB first for all spectra. Channels 4 (2 for temperature) through 254 (or 510 for x-ray data) are energy channels and contain the number of events counted within a given energy interval. The last channel of each spectrum contains the number of events with energies greater than the full scale. For the 16-bit count data, the two bytes can be converted into an integer value as follows: value = LSB + (256*MSB).

Temperatures at the instrument sensor head and on the electronics board are recorded at a 30 second interval during a measurement. These temperature data are used for internal adjustments of temperature-sensitive instrument parameters. Temperature values are stored in pairs of two 8-bit numbers with the first byte containing the electronics board temperature and the second byte containing the temperature of the sensor head. The 8-bit digital value can be multiplied by 1.442 to convert the data into Kelvin.

Table 4: MER APXS Measurement Data Components

Spectrum	Channels	Bytes	Description
X-ray	0	1-2	Lifetime in units of 10 seconds. 16-bit LSB first unsigned integer.
	1	3-4	Spectrum identifier. Incremented by one after every cycle start command or internal cycle. 12-bit LSB first unsigned integer.
	2	5-6	A0 or the multiplier for the gain. 16-bit MSB first unsigned integer. (8000 hex means 1)
	3	7-8	G or the linear term of the Temperature Compensation. 16-bit MSB first unsigned integer. (0000 hex means no TC)
	4 - 510	9-1022	Event counts; each channel is a separate energy interval. 16-bit LSB first unsigned integers.
	511	1023-1024	Overflow counts; number of events with energies greater than full scale. 16-bit LSB first unsigned integer.
Alpha1	0	1025-1026	Lifetime in units of 10 seconds. 16-bit LSB first unsigned integer.
	1	1027-1028	Spectrum identifier. Incremented by one after every cycle start command or internal cycle. 12-bit LSB first unsigned integer.
	2	1029-1030	A0 or the multiplier for the gain. 16-bit MSB first unsigned integer. (8000 hex means 1)
	3	1031-1032	G or the linear term of the Temperature Compensation. 16-bit MSB first unsigned integer. (0000 hex means no TC)
	4 - 254	1033-1534	Event counts; each channel is a separate energy interval. 16-bit LSB first unsigned integers.
	255	1535-1536	Overflow counts; number of events with energies greater than full scale. 16-bit LSB first unsigned integer.
Alpha2 (Background)	0	1537-1538	Lifetime in units of 10 seconds. 16-bit LSB first unsigned integer.
	1	1539-1540	Spectrum identifier. Incremented by one after every cycle start command or internal cycle. 12-bit LSB first unsigned integer.
	2	1541-1542	A0 or the multiplier for the gain. 16-bit MSB first unsigned integer. (8000 hex means 1)
	3	1543-1544	G or the linear term of the Temperature Compensation. 16-bit MSB first unsigned integer. (0000 hex means no TC)
	4 - 254	1545-2046	Event counts; each channel is a separate energy interval. 16-bit LSB first unsigned integers.
	255	2047-2048	Overflow counts; number of events with energies greater than full scale. 16-bit LSB first unsigned integer.
Temperature Data	0 - 255	2049-2560	Pairs of 8-bit unsigned integers. WEB temperature is the first byte, sensor head temperature is the second byte; measured at approximately 30 second intervals.

The engineering data consist of 2Kbytes of data and is located after the 12^th measurement.

Table 5: MER APXS Engineering Data Component

Channels	Bytes	Description
	1- 2	A0 TC (xray) 16-bit MSB first unsigne