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
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
69-73 Surface Pressure - .1 millibar granularity with leading blank fill '10135'
74-77 Surface Temperature - .1 degree Kelvin granularity with leading
blank fill
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
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)
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
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)
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)
123 Tropospheric Refraction Correction Indicator
0 = Data has been corrected using the Marini-Murray formula
1 = Data has not been corrected
124 Center of Mass Correction Application Indicator
0 = Applied
1 = Not applied
125 Receive Amplitude Correction Indicator
0 = Data has been receive amplitude corrected
1 = Data has not been receive amplitude corrected
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



Internal cal



Burst cal



Some other cal



Not used



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'.
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'.

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)