PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM OBJECT = TEXT PUBLICATION_DATE = 2000-06-13 NOTE = " NLR Data File Parameter Definitions " END_OBJECT = TEXT END NEAR LASER RANGEFINDER SCIENCE RECORD VARIABLES (Binary Table Fields) The following list of variable names are contained in the header of the Binary table extension of the Magnetometer data file created by CFITSIO user routines for PDS compliance. The corresponding definitions will be placed in a separate file, and will not be contained in the PDS label file, or require the generation of PDS keywords. 1. met minimum value - 0 maximum value - 160000000 units - seconds (unsigned) definition - Mission Elapsed Time in seconds for the start of this NLR Packet 2. tdb minimum value - -1.3e+8 maximum value - +6.4e+7 units - seconds (signed) definition - Barycentric Dynamical Time corresponding to MET(1). Barycentric Dynamical Time (TDB) is the independent variable in the equations, including terms for relativity, of motion of the celestial bodies. The solution of these equations gives the rectangular coordinates of those bodies relative to the barycentre (centre of mass) of the solar system. (The barycentre does not coincide with the centre of the Sun but is displaced to a point near its surface in the direction of Jupiter.) 3. dqi minimum value - N/A maximum value - N/A units - N/A definition - Data Quality Index c0 = Data Quality Flag[0=good,1=flagged for quality defects] c1 = Instrument number for FC, CTP and AIU[1 or 2] c2 - c6 = Processing Flags not quality related c7 = CCDS Source[0=VC0, 1=VC1, 2=VC2, 3=VC3] 4 and 5. CALIBRATION_WORD_1 CALIBRATION_WORD_2 minimum value - 0 maximum value - 1023 units - N/A definition - CALIBRATION_WORD_1 is the time counts for the calibration return for measurement 1 of the 56 measurements in a data packet. CALIBRATION_WORD_2 is the time counts for the calibration return for measurement 56 of the 56 measurements in a data packet. All NLR data after 6/22/00 (2000 204) will appear in the version 7 NLR format, which is the same as the version 6 normal format (ID = 4) EXCEPT for the field labeled "CALIBRATION_WORD_1" which has been changed. "CALIBRATION_WORD_1" will take the following values: in AutoAcq, "first cal" = 30 in 1 Hz, "first cal" = 584 (first shot in minor frame 4, at packet MET plus 0.5 second) in 2 Hz, "first cal" = 364 (usually) but 804 is possible. If 364, the first shot was in minor frame 2 (at packet MET plus 0.25 second). Otherwise, the first shot was in minor frame 6. 6. Spare minimum value - N/A maximum value - N/A units - N/A definition - N/A 7. T0_COUNT minimum value - 0 maximum value - 1023 units - N/A definition - The NLR receiver is 'blanked', or prevented from detecting a pulse, for a time interval T0 after the fire command. This T-0 mask is set by ground command with a default value of 180.498 ms. In-flight tests have shown that this default value, as well as values half as large, are sufficient to suppress any electronic noise from firing. The value of T0 is adjusted by two parameters returned in the NLR data; the first is called "T0_COUNT" and is represented here by the symbol d, while the second is called "Range gate" and is represented by the symbol rg. This "Range gate" parameter does not define a range gate in the usual sense of a brief time interval, during which the receiver is active, encompassing the time of the expected range return. Rather, the NLR receiver becomes active once the time T0 has elapsed, and it remains active until two stop pulses are generated, one from the calibration return and one from the target. The relation between T0 and the commandable parameters d and rg is where T0 is in units of ms, and where d and rg are both integers in the range [0, 1023] is: T0 = 0.081 +RANGE_GATE * 0.0417 + TO_COUNT*0.5 8. LAST_COMMAND minimum value - 00 Hex maximum value - 4D Hex units - N/A definition - NLR Command Op-code for the last command 9. V_THRESHOLD minimum value - 0 maximum value - 255 units - N/A definition - Threshold voltage counts. NLR's receiver is a leading-edge detector, meaning that a stop pulse is generated as soon as the optically produced signal (the filtered, analog voltage from the calibration pulse or the target return) exceeds a threshold level. 10. TIME_OF_FLIGHT_TEMP minimum value - 0 maximum value - 255 units - N/A definition - To convert counts to the time-of flight ASIC temperature ("Time-of-Flight Temp" in NLR packet data), the receiver detector temperature in C, or the medium voltage power converter temperature in C u the equation found in the calibration paper. 11. APD_BIAS minimum value - 0 maximum value - 255 units - N/A definition - To convert counts to APD bias voltage in mV ("APD Bias" in NLR packets) use the equation found in the calibration paper. 12. RANGE_GATE minimum value - 0 maximum value - 1023 units - N/A definition - See 7) T0_COUNTS definintion above. 13. PRF minimum value - 0 maximum value - 3 units - N/A definition - The laser pulse repetition rate (PRF) can be selected from among 1/8 Hz, 1 Hz, 2 Hz, and 8 Hz, but firing at 1 Hz PRF will be the nominal mode of operation at Eros. 1/8 Hz 0 1 Hz 1 2 Hz 2 8 Hz 3 14. FAIL_SAFE minimum value - 0 maximum value - 1 units - N/A definition - The NLR timing shown in Fig 2 applies to normal operation at any of the four PRF values. NLR also includes two special failure modes of operation, that can be used in the event of failures involving either the start pulse or the calibration pulse. In the former case, the FAILSAFE mode starts the TOF counters at the final value of the "T-0 COUNT" countdown. In the latter case, the ONESTOP mode causes NLR to use the first received stop pulse as the range pulse from the target. As of September, 1999, the start and c alibration pulses are functioning nominally, and there is no plan to use either FAILSAFE or ONESTOP. FAILSAFE and ONESTOP are set to 1 if in use. 15. ONE_STOP minimum value - 0 maximum value -1 units - N/A definition - See 14) FAILSAFE definition. 16. AUTO_ACQ_MODE minimum value - 0 maximum value -1 units - N/A definition - NLR has two special operating modes designed to enable autonomous operation without excessive ground commanding. The first is called "AUTO ACQUIRE", in which NLR uses the calibration pulse to find a threshold voltage above the noise level in the receiver. NLR fires 16-shot bursts at each of the eight possible values for the voltage threshold (listed in Table 1), which are labeled TH = 0 through TH = 7. AUTO_ACQ_MODE = 1 when in this mode. ========== Note: There are 56 of each of the following measurement data sets per packet. This file contains 56 columns of each, with the the index, 1-56, identifying the associated data set items. ========== 17 and 18 NORMAL_RATE_MET NORMAL_RATE_MFT minimum value - 0 maximum value - 1024 units - seconds(unsigned) definition - The 12 least significan bits of the current 32 bit Mission Elapsed Time, in seconds, for the start of this NLR measurement. MET is a 4 byte integer which is split into two items: NORMAL_RATE_MET, which is the most significant part and NORMAL_RATE_MFT, the least significant part. The range above is for the 4 byte MET. 19. NORMAL_RATE_CALIB minimum value - 0 maximum value - 1023 units - N/A definition - NLR is the first laser altimeter to employ continuous, in-flight calibration using a fiber-optic delay assembly (FODA), which is a spooled, 109.5-m fused silica fiber-optic cable. Part of each optical pulse formed within the laser resonator is injected into the FODA, which is connected to the baffle system in front of the receiver telescope. Using a 45o elliptical mirror, the delayed optical signal is directly introduced into the receiver. This allows end-to-end calibration for each emitted pulse even when no target surface is available. NORMAL_RATE_CALIB is the cal word of one shot, minus 256, expressed as unsigned integer. 20. NORMAL_RATE_TX_RDY minimum value - 0 maximum value - 1 units - N/A definition - If transmitter is ready to fire, TxReady = 0 21. NORMAL_RATE_NO_RTN minimum value - 0 maximum value - 1 units - N/A definition - If range overflow, NoReturn 22. NORMAL_RATE_RANGE minimum value - 0 maximum value - 1048508 units - N/A definition - The NLR "Range" counts are converted to integers [0, 1048580]. The conversion from "Range" counts to range is given in the calibration document. ------------------------------------------------------------------------------ NEAR KEYWORDS and Examples The following list of NEAR keywords reflects the current status and can be modified as required. EXTNAME = 'BINARY_TBL' / name of this binary table extension DATE = '06/10/98' / Current Date ORIGIN = 'NEAR-4 ' / Originator Science Data Center DATE-OBS= '19/01/98' / dd/mm/yy INSTRUME= 'NEAR-NLR' / Spacecraft Instrument AUTHOR = 'NEAR-SDC' / Contact point for this data COMMENT NEAR Project/MSI Reserved Keywords: NEAR-001 Through NEAR-199 NEAR-001= 17280 / Data offset from start of file (bytes) NEAR-002= '1.01 ' / Version of this file format NEAR-003= 'NLRN98019.FIT' / Name of this file NEAR-004= '18:00:28Z' / Time that this file was created NEAR-005= 'NLRN.001' / Product ID NEAR-006= 'PDSNLRN ' / Program name that produced this file NEAR-007= 'v0-00 ' / Version # of above program COMMENT NLR Reserved Keywords: NEAR-200 Through NEAR-299 NEAR-201= 'NLR ' / Instrument Type NEAR-202= 'NLRNORM ' / Sensor Type NEAR-203= 60595218 / Initial MET in File NEAR-204= 60602403 / Final MET in File END