urn:nasa:pds:mess_mla_calibrated:data_cdr:mlascicdr1305030818_tab 1.0 1.10.1.0 Product_Observational 2018-06-04 1.0 PDS4 migrated product. 2013-05-03T08:18:30.355Z 2013-05-03T08:40:13.230Z MESSENGER Mission urn:nasa:pds:context:investigation:mission.messenger data_to_investigation MESSENGER Spacecraft urn:nasa:pds:context:instrument_host:spacecraft.mess is_instrument_host Mercury Laser Altimeter Instrument urn:nasa:pds:context:instrument:mla.mess is_instrument Mercury Planet urn:nasa:pds:context:target:planet.mercury data_to_target Mercury Orbit Year 3 2/009893110 2/009894412 mlasciencecdr mlascicdr 2.7 mlascicdr1305030818.tab 2013-12-12T23:15:46Z 0 10424 This table contains one set of Calibrated MLA Science values, as reported by the MESSENGER Mercury Laser Altimeter (MLA). The nominal rate is 8 Hz. Additional details are contained in the CDR SIS document. Carriage-Return Line-Feed 55 0 384 et 1 1 ASCII_Real 16 second The independent variable of the equations of motion, in seconds from the J2000 epoch, at the shot timing origin T0. In the past this variable has been referred to at JPL as Ephemeris Time and at MIT, later at the Center for Astrophysics, as Coordinate Time. Its practical realization is the project-supplied clock kernel, applied to the Spacecraft Clock Mission Elapsed Time (MET) count that is transmitted to MESSENGER subsystems by the Integrated Electronics Module corresponding to the 1 PPS signal. The NAIF SPICE spacecraft clock (SCLK) kernel determines a corresponding Terrestrial Dynamic Time. These times are synchronous with respect to an observer at the Solar System barycenter in a relativistic sense. The SPICE library routine SCS2E performs the conversion to Ephemeris Time as used by the Project-supplied ephemeris files. utc 2 18 ASCII_String 24 Shot timing origin T0, converted to Coordinated Universal Time (UTC). The project-supplied clock kernel and NAIF routines convert MET into Terrestrial Dynamical Time (TDT) seconds past the J2000 epoch, and by accounting for leap seconds and the 32.184 s offset between TDT and UTC, to a standard calendar representation of UTC. met 3 43 ASCII_Integer 9 Mission elapsed time in seconds at the last 1 PPS tick. shot_number 4 53 ASCII_Integer 1 Number of 8 Hz shot or minor frame, 0-7 vga_gain 5 55 ASCII_Real 6 Commanded value for VGA gain. ch1_hi_thld 6 62 ASCII_Real 7 volt The threshold setting for channel 1 high. noise_ch1_hi 7 70 ASCII_Integer 5 Number of noise hits detected on Channel 1 high, summed over 4 shots, from plog4.4 compressed value. ch1_lo_thld 8 76 ASCII_Real 7 volt The threshold setting for channel 1 low, volts. noise_ch1_lo 9 84 ASCII_Integer 5 Number of noise hits detected on Channel 1 low, summed over 4 shots, from plog4.4 compressed value. ch2_thld 10 90 ASCII_Real 7 volt The threshold setting for channel 2, volts. noise_ch2 11 98 ASCII_Integer 5 Number of noise hits detected on Channel 2, summed over 4 shots, from plog4.4 compressed value. ch3_thld 12 104 ASCII_Real 7 volt The threshold setting for channel 3, volts. noise_ch3 13 112 ASCII_Integer 5 Number of noise hits detected on Channel 3, summed over 4 shots, from plog4.4 compressed value. tx_energy 14 118 ASCII_Real 4 millijoule Transmitted laser pulse energy. startpls_time 15 123 ASCII_Real 9 nanosecond Time of leading edge of transmit laser pulse relative to T0. startpls_width 16 133 ASCII_Real 4 nanosecond Width of transmit laser pulse in nanoseconds, used to determine centroid time of outgoing pulse. A value of 99.9 denotes a measurement whose pulse width is invalid. 99.9 range_gate_start 17 138 ASCII_Integer 5 Range gate start from RMU; units of 30 meters. range_gate_stop 18 144 ASCII_Integer 5 Range gate stop from RMU; units of 30 meters. sc_range 19 150 ASCII_Integer 5 The spacecraft range value used by the science task for algorithm calculations, in units of 30 meters per count. This value is calculated in real time by the spacecraft using its attitude and position knowledge relative to the planet. The range is provided to the instrument asynchronously at one second intervals. As soon as the science task receives a range message, it begins using the new range in its calculations. This value is an estimate only. The spacecraft range reported in telemetry may NOT be the one used throughout the entire second of algorithm calculations. ch1_hi_rx_time 20 156 ASCII_Real 10 nanosecond Time of leading edge of high threshold received laser pulse relative to T0. ch1_hi_rx_width 21 167 ASCII_Real 4 nanosecond Width of high threshold received laser pulse, used determine centroid time of return pulse. A value of 99.9 denotes a measurement whose pulse width is invalid. 99.9 wide_filt_rx_cnt 22 172 ASCII_Integer 2 Total number of wide filter low returns downlinked, a maximum is 10 (although the hardware can record up to 15 triggers). The use of multiple triggers is described in [CAVANAUGHETAL2007]. In order to compress data for telemetry, a variable length packet is issued, and this record may contain none, or up to 10, groups of event ids, times, and pulse widths. The leading and trailing event times consist of a coarse time count and a fine time count. The trailing event coarse time is downlinked as the four least significant bits of the coarse time difference. This difference should normally be zero or one depending on the phase of the return with respect to the coarse clock. The difference is sometimes one count greater than the actual difference, for reasons that are unclear, and the difference is reduced by one count, or 200 ns. If all 4 least significant bits of the coarse time difference are set, the pulse width is invalid and is set to zero. A nominal offset should be used to approximate the centroid time. Otherwise, the difference LOW_RX_WIDTH_n between leading and trailing edge event time is returned. The nominal centroid time is the leading edge time plus 1/2 this width. The FSW determines whether returns contain signal and downlinks only those low returns that are likely to be ground returns. If signal is not found by the FSW algorithm, it downlinks all triggers. Each of the triggers has a 3-bit leading and trailing edge id of 1, 2, or 4, corresponding to discriminators on filter channels 1, 2, and 3. The LOW_RX_ID_n is the logical AND of the leading and trailing ids. The RMU may occasionally issue multiple id's for an event, but the event id is that of the first valid filter channel discriminator, i.e., =0 invalid pulse, or lead and trail ID do not match. =1 channel 1 low =2 channel 2 low =4 channel 3 low. =5 pad values follow Values greater than 5 denote returns classified as non-ground, i.e., noise returns, resulting from an editing procedure. Such returns will be ignored by the subsequent Science geolocation software. The ten or fewer WIDE_FILT_RX_CNT groups of events now follow. low_rx_id_1 23 175 ASCII_Integer 1 ID for low return pulse 1. low_rx_time_1 24 177 ASCII_Real 10 nanosecond Leading edge time for low return pulse 1, if valid, relative to T0. low_rx_width_1 25 188 ASCII_Real 6 nanosecond Time difference between leading and trailing edge of low pulse 1, used to determine centroid time and spread of return pulse. low_rx_id_2 26 195 ASCII_Integer 1 ID for low return pulse 2. low_rx_time_2 27 197 ASCII_Real 10 nanosecond Leading edge time for low return pulse 2, if valid, relative to T0. low_rx_width_2 28 208 ASCII_Real 6 nanosecond Time difference between leading and trailing edge of low pulse 2, used to determine centroid time and spread of return pulse. low_rx_id_3 29 215 ASCII_Integer 1 ID for low return pulse 3. low_rx_time_3 30 217 ASCII_Real 10 nanosecond Leading edge time for low return pulse 3, if valid, relative to T0. low_rx_width_3 31 228 ASCII_Real 6 nanosecond Time difference between leading and trailing edge of low pulse 3, used to determine centroid time and spread of return pulse. low_rx_id_4 32 235 ASCII_Integer 1 ID for low return pulse 4. low_rx_time_4 33 237 ASCII_Real 10 nanosecond Leading edge time for low return pulse 4, if valid, relative to T0. low_rx_width_4 34 248 ASCII_Real 6 nanosecond Time difference between leading and trailing edge of low pulse 4, used to determine centroid time and spread of return pulse. low_rx_id_5 35 255 ASCII_Integer 1 ID for low return pulse 5. low_rx_time_5 36 257 ASCII_Real 10 nanosecond Leading edge time for low return pulse 5, if valid, relative to T0. low_rx_width_5 37 268 ASCII_Real 6 nanosecond Time difference between leading and trailing edge of low pulse 5, used to determine centroid time and spread of return pulse. low_rx_id_6 38 275 ASCII_Integer 1 ID for low return pulse 6. low_rx_time_6 39 277 ASCII_Real 10 nanosecond Leading edge time for low return pulse 6, if valid, relative to T0. low_rx_width_6 40 288 ASCII_Real 6 nanosecond Time difference between leading and trailing edge of low pulse 6, used to determine centroid time and spread of return pulse. low_rx_id_7 41 295 ASCII_Integer 1 ID for low return pulse 7. low_rx_time_7 42 297 ASCII_Real 10 nanosecond Leading edge time for low return pulse 7, if valid, relative to T0. low_rx_width_7 43 308 ASCII_Real 6 nanosecond Time difference between leading and trailing edge of low pulse 7, used to determine centroid time and spread of return pulse. low_rx_id_8 44 315 ASCII_Integer 1 ID for low return pulse 8. low_rx_time_8 45 317 ASCII_Real 10 nanosecond Leading edge time for low return pulse 8, if valid, relative to T0. low_rx_width_8 46 328 ASCII_Real 6 nanosecond Time difference between leading and trailing edge of low pulse 8, used to determine centroid time and spread of return pulse. low_rx_id_9 47 335 ASCII_Integer 1 ID for low return pulse 9. low_rx_time_9 48 337 ASCII_Real 10 nanosecond Leading edge time for low return pulse 9, if valid, relative to T0. low_rx_width_9 49 348 ASCII_Real 6 nanosecond Time difference between leading and trailing edge of low pulse 9, used to determine centroid time and spread of return pulse. low_rx_id_10 50 355 ASCII_Integer 1 ID for low return pulse 10. low_rx_time_10 51 357 ASCII_Real 10 nanosecond Leading edge time for low return pulse 10, if valid, relative to T0. low_rx_width_10 52 368 ASCII_Real 6 nanosecond Time difference between leading and trailing edge of low pulse 10, used to determine centroid time and spread of return pulse. algorithm_mode 53 375 ASCII_Integer 2 The actual algorithm mode being run. =0 Fixed Mode, =1 Spacecraft Range Mode. signal_found 54 378 ASCII_Integer 2 Indicates whether upper or lower histograms have been found by science task when processing 10 seconds worth of science data. =0 no signal. =1 upper histogram (high returns) found. =2 lower histogram (low returns) found =3 both upper and lower histogram found. sig_fram_per_super 55 381 ASCII_Integer 2 The number of frames in the superframe showing a signal. There are 5 frames per superframe. NOTE: There must be at least 4 out of 5 frames showing signal in order to have a signal based on the lower histograms. mlascicdr1305030818.lbl 0 PDS3 Original PDS3 label Carriage-Return Line-Feed