International Laser Ranging Service
10th General Assembly

Prediction Format Study Group
Agenda

San Fernando, Spain
Sunday, June 6, 2004
16:00-17:00

ILRS email exploder: ilrspfsg@ilrs.gsfc.nasa.gov
Email address listing: ilrspfsg_userlist.txt

Chairman: Randy Ricklefs
Co-chair: Jan McGarry

Chris Moore cmoore@eos-aus.com
C. (Bart) Clarke christopher.clarke@honeywell- tsi.com
Dave Rowlands drowland@helmert.gsfc.nasa.gov
David J. McClure david.mcclure@honeywell-tsi.com
Giuseppe Bianco giuseppe.bianco@asi.it
Juergen Mueller mueller@ife.uni-hannover.de
John Mck. Luck jmckluck@optusnet.com.au
Taizoh Yoshino yosh@nict.go.jp
Ulrich Schreiber schreiber@wettzell.ifag.de
Werner Gurtner werner.gurtner@aiub.unibe.ch
Graham Appleby graham.appleby@nerc.ac.uk
Jan F. McGarry jan.mcgarry@gsfc.nasa.gov
Julie E. Horvath julie.horvath@honeywell-tsi.com
Randall Ricklefs ricklefs@csr.utexas.edu
Richard J. Eanes eanes@csr.utexas.edu
Wu Wang wang_wu0@sina.com
yozxs@public.km.yn.cn

1. SLR
   • 4 partial passes taken at MLRS using new format (2 Lageos-2, one BEC, and one Ajisai)
   • CPF files were derived from HTSI TIVs with 60 sec step size
   • Normal point program used state vector from start of pass. Will be converted to use CPF
   • MLRS acquisition software can handle both TIV-derived polynomials and CPF, allowing crews to quickly switch between prediction types.
   • Awaiting NSGF predictions
2. LLR
   • MLRS acquisition software has been modified to accept CPF for lunar ranging
   • Bench checking/simulations complete, awaiting real tracking
   • MLRS lunar prediction code has been modified to produce CPF multi-day files:
   1. One file for each reflector
   2. One file for center of moon
   3. Center of moon file also contains librations (euler) angles and Greenwich apparent sidereal time to allow pointing to arbitrary lunar surface coordinates
3. Transponders
   • MGS predictions using center of earth to spacecraft vectors give agreement to about 10m.
   • Translating to topocentric coordinates raises this error
   • No field test anticipated, except to verify capability
4. Notes
   MLRS acquisition code does not handle LLR and SLR with same routines. It is possible to do this, but will require a great deal of time and testing.

1. Audit cpf file for correct entries and combination of elements
   • Needed especially for prediction centers
   • Does not yet exist. Any takers?
2. Split tabular body-fixed files into pass-by-pass tabular body-fixed files for a give station.
   • Needed for acquisition software and for scheduling
   • Program called tab_split
   • Based on HTSI programs ivsaer and facqmes
   • Used in MLRS testing
3. Create a schedule
• Used HTSI code persight/facqmes/schedule
4. Test-bed: ilrspred
   • Input is long CPF file
   • Outputs pass-length files with topocentric az/el/range, outbound and inbound at user-specified intervals

1. Format modifications since last meetings
   • EOP data, reduction of prediction center field to 4 characters, addition of option for inertial vectors, etc. were all added based on the results of the last meeting.
   • Records to include offset of the target from the target center of mass and body rotation angles (record types 51/52 and 60, respectively) were also added.
   • Expanded explanations and literature references were added to the working document.
2. The format seems to have the required fields
   • Cannot test many of transponder-specific fields
   • Rotation angle record gives Euler libration angles phi, theta, and psi for the moon, but what for other planets? Are alpha-0, delta-0 and W adequate?
   • Is the offsets field OK as is?
   • Have not tested the inertial/space fixed options. Have added GAST and EOP fields to accommodate conversion to/from inertial space.
   • There are plenty of un-designated record numbers in case additions are needed. There is also a format version number.
   • Having someone else write the CPF file audit program should help expose inconsistencies and ambiguities in the document.
   • Some ambiguities and multiple ways of doing the same thing are good, as long as field software can accommodate it.
3. The working document needs help
   • Much more thorough that before, but needs more work
   • Is this the best document for field installation?

1. sample code
   • Complete working version
   • Make first release of sample code to NSGF, EOS
   • Start 'C' version of sample code (EOS)
   • Need a format validation program for prediction producers (and maybe a verification data set for prediction users)
2. Continue documenting algorithms
3. produce metrics for prediction accuracy
4. Field tests
   • MLRS to continue
   • NSGF?
   • EOS?
   • Others?

Appendix A...

1) Data headers

Header type 1 Basic information - 1 (required)
 1-2    A2      Record Type (= "H1")
 4-6    A3      "TAB"
 8-9    I2      Format Version
11-14   A4      Ephemeris Source (e.g., "HTSI ", "UTX ")
16-19   I4      Year of ephemeris production
21-22   I2      Month of ephemeris production
24-25   I2      Day of ephermeris production
27-28   I2      Hour of ephemeris production (UTC)
30-34   I5      Ephemeris Sequence number
36-45   A10     Notes (e.g., "041202","DE-403")

Header type 2 Basic information - 2 (required)
 1-2    A2      Record Type (= "H2")
 4-11   I8      COSPAR ID
13-16   I4      SIC
18-25   I8      NORAD ID
27-30   I4      Starting Year
32-33   I2      Starting Month
35-36   I2      Staring Day
38-39   I2      Starting Hour (UTC)
41-42   I2      Starting Minute (UTC)
44-45   I2      Starting Second (UTC)
47-48   I2      Ending Day
50-51   I2      Ending Hour (UTC)
53-54   I2      Ending Minute (UTC)
56-57   I2      Ending Second (UTC)
59-63   I5      Time between table entries (UTC seconds)(=0 if variable)
65      I1      Compatibility with TIVs = 1 (=> integratable, geocentric ephemeris)
67      I1      Target type
                        1=passive artificial satellite
                        2=passive lunar reflector
                        3=synchronous transponder
                        4=asynchronous transponder
 69     I2      Reference frame
                        0 =geocentric body fixed (default)
                        1=geocentric space fixed (i.e. Inertial) (True of Date)
                        2=geocentric spare fixed (Mean of Date J2000)
                        3=...

Header type 4 Expected accuracy (="H3")
 4-8    I5      Along-track run-off after 0 hours (meters)
10-14   I5      Cross-track run-off after 0 hours (meters)
16-20   I5      Radial run-off after 0 hours    (meters)
22-26   I5      Along-track run-off after 6 hours (meters)
28-32   I5      Cross-track run-off after 6 hours (meters)
34-38   I5      Radial run-off after 6 hours    (meters)
40-44   I5      Along-track run-off after 24 hours (meters)
46-50   I5      Cross-track run-off after 24 hours (meters)
52-56   I5      Radial run-off after 24 hours (meters)

Header type 5 Transponder information
 1-2    A2      Record Type (= "H4")
 4-15   F12.5   Pulse Repetition Frequency (PRF) in Hz
17-26   F10.4   Transponder transmit delay in microseconds
28-38   F11.2   Transponder UTC offset in microseconds
40-50   F11.2   Tranponder Oscillator Drift in parts in 1015

Header type 9 Last header record
 1-2    A2      Record Type (= "H9")

2) Ephemeris entry (repeat as needed)

Record type 1 Position (transmit required for all targets; receive for distant targets and transponders)

 1      A1      Record Type (= '1')
 2      A1      Direction flag (transmit = 1; receive = 2)
        1x
        I5      Modified Julian Date (MJD)
        1x
        f12.5   Seconds of Day (UTC) (Transmit or receive depending on direction flag)
        1x
        I2      Leap second flag (= the value of the new leap second if introduced)
        1x
        f17.3   Geocentric X position in meters
        1x
        f17.3   Geocentric Y position in meters
        1x
        f17.3   Geocentric Z position in meters

Record type 2 Velocity (tranmit required for all targets; receive for distant targets and transponders)

 1      A1      Record Type (= '2')
 2      A1      Direction flag (transmit = 1; receive = 2)
        1x
        f19.6   Geocentric X velocity in meters/second
        1x
        f19.6   Geocentric Y velocity in meters/second
        1x
        f19.6   Geocentric Z velocity in meters/second

Record type 3 Corrections (all targets computed from a solar system ephemeris)

 1      A1      Record Type (= '3')
 2      A1      Direction flag (transmit = 1; receive = 2)
        1x
        F18.6   X stellar aberration correction in meters
        1x
        F18.6   Y stellar aberration correction in meters
        1x
        F18.6   Z stellar aberration correction in meters
        1x
        F5.1    Relativistic range correction in nsec (positive number)

Record type 4 Transponder specific (Transponders)

 1-2    A2      Record Type (= '40')
        1x
        F6.3    Oscillator relativity correction in meters/second

Record type 5 Offset from center of main body (Surface features and satellites)

 1      A1      Record Type (= '5')
 2      A1      Direction flag (transmit = 1; receive = 2)
        1x
        I5      Modified Julian Date (MJD)
        1x
        f12.5   Seconds of Day (UTC)
        1x
        a10     Name of target (no spaces in middle)
        1x
        f17.3   X position offset in meters
        1x
        f17.3   Y position offset in meters
        1x
        f17.3   Z position offset in meters

Record type 6 Rotation angle of offset (Surface features)

 1-2    A2      Record Type (= '60')
        1x
        I5      Modified Julian Date (MJD)
        1x
        f12.5   Seconds of Day (UTC)
        1x
        f17.12  Rotation angle 1 in degrees (For moon: Phi)
        1x
        f17.12  Rotation angle 2 in degrees (For moon: Theta)
        1x
        f17.12  Rotation angle 3 in degrees (For moon: Psi)
        1x
        f17.12  Greenwich Apparent Sidereal Time in hours

Record type 7 Earth orientation (for space-fixed mode,
                as needed, typically one a day)

 1-2    A2      Record Type (= '70')
        1x
        I5      Modified Julian Date (MJD)
        1x
        I6      Seconds of Day (UTC)
        1x
        F7.4    X pole (degrees)
        1x
        F7.4    Y pole (degrees)
        1x
        F10.5   dUTC (seconds)

Record type 9 Last ephemeris record
 1-2    A2      Record Type (= "99")

3) Comments

 1      A2      Record Type (="00")
 3-80   A       Free format comments
		

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