Time Dependent Parameters (tdp files)

There are two possible tdp formats, one for files, and another a binary record format used in shared memory (sometimes directly converted into packets for network transport):

1. ASCII file - suggested suffix .tdp[.gz]
2. Binary record

Time Dependent Parameter files describe a time series of values. The file must be time ordered (earliest times first).

TimeDepParmsReader is C++ reader and interpolator - see it for details on interpolation and extrapolation options.

Note for GCORE parameters the units follow gcore convention:

Internal units are MKS (meter, kilogram, second), angles are in radians. For example: YawRate values are in radians/second. Note that Clock Units are in meters. If you are uncertain of the units, contact the GipsyX team.

Parameter names in tdp files follow GipsyX naming conventions which use ".", to separate tree like structures of their names, for instance Satellite.E202.Clk.Bias is the clock correction for the Galileo satellite E202.

GCORE/bin/goaTdp2rtg.py provides a limited conversion utility for GIPSY II to GCORE.

The Source.ID records information on the exact process that computed the values on the file for internal JPL use.

(1) ASCII file This file consists of a series of lines with space delimited fields. Each line has the following fields:

time nominal_value value sigma(flag) name

where:

1. time continuous seconds past Jan. 1, 2000 11:59:47 UTC. GCORE standard for time
2. nominal_value a nominal value for the parameter
3. value value at the given time
4. sigma standard deviation for the parameter
5. name An arbitrary sequence of letters [A-Z,a-z], digits[0-9], and "." without spaces.

Comment lines may be entered by having the first non-whitespace character be a "#". Blank lines, consisting only of whitespace, are ignored.

Example: GPS clocks

375958800.0000  0.00000000000000  -110937.208992753  0.0368   .Satellite.GPS23.Clk.Bias  
375958800.0000  0.00000000000000  -29353.6260510073  0.03289  .Satellite.GPS55.Clk.Bias  
375958800.0000  0.00000000000000  -56334.9377148186  0.02548  .Satellite.GPS45.Clk.Bias  
375958800.0000  0.00000000000000  -6204.53013079112  0.03307  .Satellite.GPS40.Clk.Bias  
375958800.0000  0.00000000000000  -62620.3640976035  0.0237   .Satellite.GPS46.Clk.Bias  
375958800.0000  0.00000000000000  -63071.7717481915  0.02545  .Satellite.GPS59.Clk.Bias  
375958800.0000  0.00000000000000  -63439.1644293312  0.03634  .Satellite.GPS56.Clk.Bias
...   

(2) Binary record

Binary TDP records take the following form, with all variables in native Linux (little-endian) formatting.

As above, for GCORE the values and sigmas are in physical MKS units (angles in radians)

8 bytes: uint64_t = total record size = 64 + <name_size>
8 bytes: uint64_t = version = 1
8 bytes: int64_t = integer part of ttag
8 bytes: double = fractional part of ttag n.b. doesn’t appear separately in dump
8 bytes: double = nominal value
8 bytes: double = estimated value
8 bytes: double = sigma
8 bytes: uint64_t = <name_size> = size of <parameter_name> string
<name_size> bytes: actual <parameter_name> string
 
for example, the total size = 84 + <sat_name_size> bytes for satellite clock parameters of the form
  <parameter_name> = ".Satellite.<sat_name>.Clk.Bias"