International Laser Ranging Service

ILRS Full-Rate Data Format (V3)

(Formerly known as MERIT II)

Bytes	Description	Example
1-7	ILRS Satellite Identification Number - 7 digit number based on COSPAR ID, See Explanation	'7603901'
8-9	Year of Century - 2 digits with leading zero fill	'09'
10-12	Day of Year - 3 digits with leading blank fill	' 34'
13-24	Time of Day - from midnight GMT with a .1 microsecond granularity and leading blank fill	' 36005000000'
25-28	Crustal Dynamics Project Pad ID- a 4-digit monument identification	'7105'
29-30	Crustal Dynamics Project 2-digit system number	'07'
31-32	Crustal Dynamics Project 2-digit occupancy sequence number	'24'
33-39	Azimuth - the geometric or true azimuth angle with a .1 millidegree granularity and leading blank fill	' 987500'
40-45	Elevation - the geometric or true elevation angle with a .1 millidegree granularity and leading blank fill	'292500'
46-57	Laser Range - in units of two way time with a 1 picosecond granularity and leading blank fill	' 52035998000'
58-64	Pass RMS from the mean of raw range values minus the trend function, for accepted ranges (two-way value in picoseconds).	'     66'
65-68	Wavelength of the laser with leading blank fill The user of the data should interpret the value given as follows: 3000 - 9999: units are 0.1 nanometer 1000 - 2999: units are 1.0 nanometer For the station generating the data, the rule is: Wavelength in rate 0.3000 - 0.9999 microns: unit 0.1 nanometer Wavelength in rate 1.000 - 2.999 microns: unit 1.0 nanometer	'5321'
69-73	Surface Pressure - .1 millibar granularity with leading blank fill	'10135'
74-77	Surface Temperature - .1 degree Kelvin granularity with leading blank fill	'2905'
78-80	Relative Humidity at Surface - percentage with leading blank fill	' 55'
81-85	Tropospheric refraction correction - a round trip refraction correction with a 1 picosecond granularity and leading blank fill	'33956'
86-91	Center of Mass Correction - a round trip correction with a 1 picosecond granularity and leading blank fill	'   1601'
92-96	Receive Amplitude - a positive linear scale value with leading blank fill	'  700'
97-104	Applied System Delay - the two way system delay applied in the current record with a 1 picosecond granularity and leading blank fill	' 95942'
105-110	Calibration Delay Shift - a measure of two way calibration stability with a 1 picosecond granularity and leading blank fill.	'    33'
111-114	Root Mean Square (RMS) of raw system delay values from the mean. Two-way value in picoseconds. If pre- and post- pass calibrations are made, use the mean of the two RMS values, or the RMS of the combined data set.	'   40'
115	Normal Point Window Indicator - indicates whether or not the record represents a normal point and the time span of the normal point 0: not a normal point 1: 5-second normal point (GFZ-1) 2: LLR normal point 3: 15-second normal point (TOPEX) 4: 20-second normal point 5: 30-second normal point 6: 1-minute normal point 7: 2-minute normal point (LAGEOS) 8: 3-minute normal point 9: 5-minute normal point (ETALON)	'0'
116-119	Number of raw ranges compressed into normal point leading blank fill	'    '
120	Epoch Event - indicates the time event reference. Currently, only 1 and 2 are used for laser ranging data. 0 = Ground receive time 1 = Satellite transmit time (standard for LAGEOS) 2 = Ground transmit time 3 = Satellite receive time	'1'
121	Epoch Time Scale - indicates the time scale reference. Other flags may appear for historical data. 3 = UTC (USNO) 4 = UTC (GPS) 7 = UTC (BIH)	'3'
122	Angle Origin Indicator - source of angle values. 0 = Unknown (converted from MERIT I) 1 = Computed (from range) 2 = Command (predicts and operator inputs) 3 = Measured (calibrated instrument readings)	'3'
123	Tropospheric Refraction Correction Indicator 0 = Data has been corrected using the Marini-Murray formula 1 = Data has not been corrected	'0'
124	Center of Mass Correction Application Indicator 0 = Applied 1 = Not applied	'0'
125	Receive Amplitude Correction Indicator 0 = Data has been receive amplitude corrected 1 = Data has not been receive amplitude corrected	'1'
126	System calibration method and delay shift indicator. Indicates the type of calibration and the type of calibration shift given in columns 105-110 Pre- to Post-Pass Calibration Shift Minimum to Maximum Calibration Shift External cal 0 5 Internal cal 1 6 Burst cal 2 7 Some other cal 3 8 Not used 4 9	'0'
127	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.	'0'
128	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).	'1'
129	Format Revision Number Indicator - indicates the version of the MERIT II format for the current record. Data prior to MERIT II that is converted into the MERIT II format will have a revision number of '0'.	'3'
130	Release Flag Indicator - indicates when this record first appeared on a release tape. Cooperating stations which send release tapes to the CDDIS will use a numbering scheme beginning with '1'. Release tapes from the CDDIS will have a labelling scheme beginning with 'A'. Non-operational engineering data will have a release flag of 'Z'. Data released prior to the MERIT II implementation will have a release flag of '0'.	'A'

Specifications on the Fullrate format:

1) A field should be blank if a value does not apply or if the value is unknown.
2) All fields should have trailing '0' fill when the accuracy of the field value is less than the accuracy of the format.
3) The range and all correction fields are in two way time units of picoseconds for both accuracy and consistency.
4) All correction field values, except the center of mass, are represented such that they would be subtracted from the laser range when applied. The center of mass value is represented such that it would be added to the laser range when applied.
5) To convert the laser range field from two way time in picoseconds to one way distance in meters:

a) convert the range in units of picoseconds to seconds
b) divide the result in a) by 2
c) multiply the result in b) by the speed of light, (299792458 m/s)