ILRS Full-Rate Data Format (V2)

(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 Laser Range Standard Deviation - in units of two way time with a
1 picosecond granularity and leading blank fill 		'     66'
65-68 Wavelength - .1 nanometer granularity with leading blank fill '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 Calibration Standard Deviation - in units of two way time with a
1 picosecond granularity and leading blank fill 		'   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 = Range not a normal point
2 = 10 second normal point
3 = 15 second normal point
4 = 20 second normal point
5 = 30 second normal point
6 = 1 minute normal point (historical data only)
7 = 2 minute normal point
8 = 3 minute normal point (historical data only)
9 = 5 minute normal point 		'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)
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 Indicator
0 = External Calibration
1 = Internal Calibration
2 = Burst Calibration
3 = Override Calibration 		'0'
127 Calibration Delay Shift Indicator - specifies the type
of delay shift represented in columns 105 to 110
0 = Pre to Post shift
1 = Peak to Peak shift 		'0'
128 System Configuration Flag Indicator - is a flag to be
incremented for every major system configuration change.
The flag will be initially set at '1' at the time of MERIT II
implementation. Data prior to MERIT II that is converted
into the MERIT II format will have a flag of '0'.		 '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'. 		'2'
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) The possible historical values for the Epoch Time Scale field are as follows:

    0 = UT0
    1 = UT1
    2 = UT2
    3 = UTC (USNO)
    4 = A.1 (USNO)
    5 = TAI
    6 = A-S (Smithsonian)
    7 = UTC (BIH)
    8 = Unassigned
    9 = Other

6) 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)