Historic Normal Point Format Details

This page describes the historic ILRS normal point format; as of March 2012 the ILRS uses the Consolidated Data Format (CRD) for both normal point and full-rate data. Fields revised in March 1997 are shown in blue. Fields revised in August 2004 to accomodate kHz ranging data are shown in yellow.

Header Record
(Revision 1 - March 1997)
(Revision 2 - August 2004)

Column

Description

Example
1-7 ILRS Satellite identifier - 7-digit identification number (based on COSPAR) See Note below:

'7603901'
8-9 Year of century

'89'
10-12 Day of year

'079'
13-16 Crustal Dynamics Project Pad ID- a 4-digit monument identification

'7105'
17-18 Crustal Dynamics Project 2-digit system number

'07'
19-20 Crustal Dynamics Project 2-digit occupancy sequence number

'02'
21-24 Wavelength of the laser
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'
25-32 Calibration system delay (two-way value in picoseconds)

'00095942'
33-38 Calibration delay shift (two-way value in picoseconds)

'000033'
39-42 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.

'0040'
43 Normal Point window indicator (an integer from 0 to 9)
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)

'7'
44 Epoch time scale indicator
3: UTC (USNO)
4: UTC (GPS)
7: UTC (BIPM) (BIH prior to 1988)

'3'
45 System calibration method and delay shift indicator. Indicates the type of calibration and the type of calibration shift given in columns 33-38

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'
46 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'
47 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'
48-51 Pass RMS from the mean of raw range values minus the trend function, for accepted ranges (two-way value in picoseconds).

'0065'
52 Data quality assessment indicator
For LLR data:
0: Undefined or no comment.
1: Clear, easily filtered data, with little or no noise.
2: Clear data with some noise; filtering is slightly compromised by noise level.
3: Clear data with a significant amount of noise, or weak data with little noise. Data are certainly present, but filtering is difficult.
4: Un-clear data; data appear marginally to be present, but are very difficult to separate from noise during filtering. Signal to noise ratio can be less than 1:1.
5: No data apparent.

'0'
53-54 Checksum - an integer value equal to the sum of integers in columns 1-52, modulo 100 (optional)

'53'
55

Format revision number indicator.
Value '1' for the 1997 revision. Implied value '0' or 'space' for original 1990 release.
Revision 2 and above, use byte 49 in data record to indicate power of ten with which to multiply the number stored in bytes 44-47 of data record.

'2'

Note: COSPAR ID to ILRS Satellite Identification Algorithm

COSPAR ID Format: (YYYY-XXXA)

YYYY is the four digit year of when the launch vehicle was put in orbit
XXX is the sequential launch vehicle number for that year
A is the alpha numeric sequence number within a launch
Example: LAGEOS-1 COSPAR ID is 1976-039A
Explanation: LAGEOS-1 launch vehicle wasplaced in orbit in 1976; was the 39th launch in that year; and LAGEOS-1 was   the first object injected into orbit from this launch.

ILRS Satellite Identification Format: (YYXXXAA), based on the COSPAR ID

Where YY is the two digit year of when the launch vehicle was put in orbit
Where XXX is the sequential launch vehicle number for that year
AA is the numeric sequence number within a launch
Example: LAGEOS-1 ILRS Satellite ID is 7603901

Data Record
(Revision 1 - March 1997)
(Revision 2 - August 2004)

Column

Description

Example
1-12 Time of day of laser firing, from 0 hours UTC in units of 0.1 microseconds.
Value is given module 864000000000 if pass crosses 24 hours UTC

'214360786545'
13-24 Two-way time-of-flight corrected for system delay, in picoseconds. Not corrected for atmospheric delay, nor to the center-of-mass of the satellite.

'052035998000'
25-31 Bin RMS from the mean of raw range values minus the trend function, for accepted ranges. Two-way value in picoseconds. If point is a single raw data point, then use pass RMS.

'0000066'
32-36 Surface pressure, in units of 0.1 millibar

'10052'
37-40 Surface temperature in units of 0.1 degree Kelvin

'2932'
41-43 Relative humidity at surface in percent

'092'
44-47 Number of raw ranges (after editing) compressed into the normal point. See Note 1: below

'0108'
48 A flag to indicate the data release:
0: first release of data
1: first replacement release of the data,
2: second replacement release, etc.

'0'
49 For SLR data: not used before revision 2. Revision 2 and above, indicates power of ten with which to multiply number stored in bytes 44-47 in order to provide a very close approximation to the total number of returns for high yield systems (kHz systems).
For LLR data: integer seconds of the two-way time of flight (columns 13-24 contain the fractional part).

'2'
50 For SLR data: not used
For LLR data: normal point window indicator. Indicates the time span of the normal point (can be variable from point to point).
1: <= 5 minutes
2: 10 minutes
3: 15 minutes
4: 20 minutes
5: 25 minutes
6: 30 minutes
7: 35 minutes
8: 40 minutes
9: >= 50 minutes

'1'
51-52 For SLR data: not used
For LLR data: signal to noise ratio, in units of 0.1, e.g.,
00: No information
01: Signal/noise = 0.1
...
99: Signal/noise = 9.9 or greater

'00'
53-54 Checksum - integer value = to the sum of digits in columns 1-52, modulo 100 (optional)

'51'

Note 1: In September 1999, the Jaguar Team concluded "That ILRS make NO RESTRICTION on the minimum number of returns used to generate Normal Points."

Sampled Engineering Data Record
(last change December 1995)

Column

Description

Example
1-12 Time of day of laser firing, from 0 hours UTC, in units of 0.1 microseconds

'214360786545'
13-24 Two-way time of flight with no corrections applied, in picoseconds

'052035998000'
25-29 Surface pressure, in units of 0.1 millibar

'10052'
30-33 Surface temperature in units of 0.1 degree Kelvin

'2932'
34-36 Relative humidity at surface in percent

'092'
37-44 Internal burst calibration system delay.

'00003124'
45-48 Relative signal strength for the return (unit of measure determined by individual stations).

'0789'
49 Angle origin indicator - source of angle values in columns 50-62:
0: Unknown
1: Computed (from range)
2: Command angles - predicted angles with refraction correction and crew biases, if any, applied
3: Measured angles - encoder readings with mount model corrections removed to give actual azimuth and elevation as affected by refraction

'3'
50-56 Azimuth angle in units of 0.0001 degree, using local reference system (north 0, east = 90)

'0981501'
57-62 Elevation angle in units of 0.0001 degree, using local reference system (zenith = 90)

'292501'
63-67 Unused (zero-filled)

'00000'
68-69 Checksum - an integer value equal to the sum of the digits in columns 147, module 100

'07'