Home
Introduction
HGS-1 Rescue
Year 2000
Executive Summary
MicroCosm® and GNSS
MicroCosm® GNSS Prep
Timing Comparisons
Operating Environment
Other Information
Sign In
Pricing Information
Contact VMSI
Distributors
Links

MicroCosm® Support Programs

 

MicroCosm® Eclipse

 

MicroCosm® Eclipse is a support program which reads a MicroCosm® Trajectory File and produces a table of changes in spacecraft shadowing by the Earth and the Moon. For each spacecraft contained on the input trajectory file, MicroCosm® Eclipse outputs the date & time, the spacecraft position, the percent of Earth shadowing and the percent of Lunar shadowing at the initial epoch. At subsequent epochs, the same quantities are output whenever the percentage of either Earth or Lunar shadowing changes.

Eclipse Input

Control of MicroCosm® Eclipse is via an ASCII file which specifies the input MicroCosm® Trajectory File name. The input trajectory file must be in "MicroCosm® Trajectory File Format" as described in MicroCosm® POD documentation Volume 2, "MicroCosm® POD File Descriptions" Section 4.1. The option to request Lunar and Solar positions on the trajectory file must be exercised in the MicroCosm® Control setup (option ORBFIL).

Eclipse Outputs

Output from MicroCosm® Eclipse is written to Standard Output. Spacecraft positions will be Earth Centered Fixed (ECF) or Earth Centered Inertial (ECI) coordinates depending upon the options exercised in MicroCosm® Control (option ORBFIL). If ECF coordinates are present on the trajectory file, output will be in ECF, otherwise output will be in ECI. Trajectory epochs will be given in calendar date and UTC time.

The MicroCosm® Eclipse Program is available as an extra cost option to the MicroCosm® POD Software and is subject to the same software license terms as the MicroCosm® POD Software.

 

MicroCosm® FormSP3 Program

 

MicroCosm® FormSP3 is a support program which reads a MicroCosm® Trajectory File and produces a spacecraft trajectory file in "The Standard Format SP3" as documented by Spofford and Remondi. To allow this format to accommodate non-GNSS as well as GNSS space vehicles (SV's), VMSI has defined an extension of the format which utilizes the comment records (SP3 Lines 19-22) as needed to define seven digit SV ID's for non-GNSS SV's. The MicroCosm® FormSP3 Program is available as an extra cost option to the MicroCosm® POD Software and is subject to the same software license terms as the MicroCosm® POD Software.

FormSP3 Inputs

Control of FormSP3 is via an ASCII file which specifies the input MicroCosm® Trajectory File name, the output SP3 File name and permits the user to override the SP3 header records and specify position-only or position & velocity output. The input trajectory file must be in "MicroCosm® Trajectory File Format" as described in MicroCosm® POD documentation Volume 2, "MicroCosm® POD File Descriptions" Section 4.1.

FormSP3 Outputs

The MicroCosm® FormSP3 Software executes from the operating system prompt, prints a copyright notice upon execution and will return the system prompt upon completion. The MicroCosm® Trajectory File contains spacecraft position (meters) and velocity (meters/second) in either Earth Centered Fixed (ECF) or Earth Centered Inertial (ECI) coordinates and time in ET (TDT). When ECF coordinates are unavailable, FormSP3 transforms the ECI coordinates to ECF using the Right Ascension of Greenwich and Rotation Rate of the Earth, ignoring the effects of polar motion. The trajectory file output may contain positions-only or both positions & velocities and conforms to the "The Standard Format SP3" as documented by Spofford and Remondi1.


1"The Standard Format SP3", Spofford, Paul R., Benjamin W. Remondi, 6 February 1995, National Oceanic and Atmospheric Administration, National Geodetic Survey.

 

MicroCosm® NavMsg

 

MicroCosm® NavMsg is a set of two support programs, NavMsg and SP3Clock, which operate on spacecraft trajectory files that have been generated in SP3 or SP3c format. The NavMsg program creates RINEX Navigation files from definitive or predictive GNSS trajectory solutions. The SP3Clock program determines linear or quadratic clock polynomials which span multiple SP3 trajectory files. Normally RINEX Navigation files contain Broadcast Ephemeris. However, NavMsg provides the user with the capability of converting the IGS precise ephemeris, the IGS Rapid Ephemeris, the IGS Ultra-rapid Ephemeris or IGS GLONASS Ephemeris into RINEX GPS Navigation format. Precise ephemeris determined by the MicroCosm® POD Software and converted to SP3 format by MicroCosm® FormSP3 may also be converted to RINEX GPS Navigation format by NavMsg.

NavMsg Inputs

Operations of NavMsg and SP3Clock are controlled using command line switches which follow the UNIX convention and provide the user with the capability of specifying the input SP3 or SP3c trajectory file path/name, overriding the default print file path/name, overriding the default output RINEX Navigation file path/name and selecting definitive trajectory, predictive trajectory or both for output to RINEX Navigation file format. GPS broadcast ephemeris navigation parameters are typically updated every two hours and are valid for four hours. The user may specify the duration of the navigation parameter fit.

NavMsg Outputs

NavMsg and SP3Clock use the input SP3 or SP3c trajectory file positions and clock offsets as observations in least squares solutions of a linear model of clock variations and for the estimation of the GPS Broadcast Ephemeris model parameters. Therefore, in addition to RINEX Navigation files, the output from NavMsg and SP3Clock includes residuals and iterative residual summaries of these least squares solutions.

MicroCosm® NavMsg is available as an extra cost option to the MicroCosm® POD Software or as standalone programs operating independently from the MicroCosm® POD Software. Licensees of MicroCosm® NavMsg Executables must complete two copies of "SOFTWARE LICENSE AGREEMENT MicroCosm® NavMsg Executables. " Licensees of MicroCosm® NavMsg Limited Source Code must complete two copies of "SOFTWARE LICENSE AGREEMENT MicroCosm® NavMsg Source Code." The full text of these licenses is available in "Portable Data Format" (PDF) which is readable using the Adobe Acrobat Reader. If you do not have Acrobat Reader, it may be downloaded for free from the Adobe web site at www.adobe.com. The MicroCosm® license PDF files may be viewed and/or downloaded by following the links for MicroCosm® NavMsg Executables License or MicroCosm® NavMsg Source Code License.

 

MicroCosm® Orb_Diff Program

 

MicroCosm® Orb_Diff is a support program which operates on spacecraft trajectory files generated by the MicroCosm® POD Software. Its function is to create a file of differences between multiple spacecraft trajectory files which have been generated by the MicroCosm® POD Software. The MicroCosm® Orb_Diff Program is available as an extra cost option to the MicroCosm® POD Software and is subject to the same software license terms as the MicroCosm® POD Software.

Orb_Diff Inputs

Input to Orb_Diff is via a file list ("filist.odf"), the MicroCosm® earth rotation tables (as described in MicroCosm® POD documentation Volume 2, "MicroCosm® POD File Descriptions", Section 2.5) and an ASCII control file. Multiple pairs of trajectory files may be specified for differencing by Orb_Diff. Each trajectory file must be in "MicroCosm® Trajectory File Format" as described in MicroCosm® POD documentation Volume 2, "MicroCosm® POD File Descriptions" Section 4.1. No interpolation is performed by Orb_Diff. Therefore, the trajectory files to be differenced must be generated with a common set (or subset) of trajectory epochs. The interval between epochs to be differenced must be specified as an integral multiple of the intervals between epochs on the trajectory files to be differenced.

Orb_Diff Outputs

Output from Orb_Diff is an ephemeris of trajectory differences in Cartesian (XYZ) position and radial, cross track and along track (RCL) position. Differences are specified in meters with a least significant digit of 0.001 meters. Time is specified as UTC calendar date and time of the first epoch with elapsed minutes for each subsequent epoch. Column headings and other identifying information precede the differences for each satellite from each pair of trajectory files. Multiple trajectory file differences are all concatenated onto a single ASCII output file.

 

MicroCosm® Res_Edit Program

 

MicroCosm Res_Edit is a support program which operates on an Observation Residual file generated by the MicroCosm POD Software. Its function is to use the observation data and observation correction data optionally contained in the MicroCosm Observation Residual file to create an edited observation file in MicroCosm Binary Tracking Data Format. Editing (i.e. removal of observations) is performed based upon four criteria:

  • Data edited by the MicroCosm POD Software are removed from observation data blocks;

  • Measurement pairs are removed from observation data blocks if either member of the pair was edited by the MicroCosm® POD Software (Angular data types such a azimuth & elevation are treated as pairs by the MicroCosm POD Software.);

  • Entire observation data blocks are deleted, if after editing with the above criteria,they contain fewer than a user specified number of weighted observations (or observation pairs); and

  • Entire observation data blocks are deleted which contain fewer than a user specified total number of observations (or observation pairs).

Res_Edit Inputs

Input to Res_Edit is via a file list ("filist.res"), an optional ASCII control file, and a MicroCosm Observation Residual File.

Res_Edit Outputs

Output from Res_Edit consists of a small number of lines printed on the standard output device and an observation data file in "MicroCosm Binary Tracking Data Format".

MicroCosm® Res_Edit Program is available as an extra cost option to the MicroCosm® POD Software and is subject to the same software license terms as the MicroCosm® POD Software.

 

MicroCosm® Sim_Soft

 

The MicroCosm® Simulation Software, MicroCosm® Sim_Soft, consists of a group of programs that depend upon outputs from the MicroCosm® POD Software to create simulated data and then to introduce model errors into otherwise "model perfect" data. A series of steps are performed to accomplish these goals.

  • MicroCosm® Control and MicroCosm® Executive are invoked to generate the trajectories of the spacecraft involved.

  • The MicroCosm® GNSS_Gen program may be used to generate simulated GNSS observations in the RINEX-2 data format and/or the MicroCosm® Obs_Gen program may be used to generate simulated laser or radar tracking observations in the GEODYN Binary Format. These simulated observations are only approximate, but do represent the correct spacecraft visibilities.

  • GNSS data are then processed through the MicroCosm® GNSS Data Formatter (GDF) and other data are processed through the MicroCosm® Tracking Data Formatter (TDF). If both kinds of data are produced, then they are merged together before proceeding with the next phase.

  • MicroCosm® Control and MicroCosm® Executive are then invoked again, but in "Simulated Data Mode" (Volume 3, "MicroCosm® POD Operations Description", Global Option SIMDAT). When used in this manner, these programs will cause the "observed" measurements (those created by GNSS_Gen and Obs_Gen) to be replaced by the computed, or "model perfect", measurements.

  • The "model perfect" measurements output by the previous step are then processed through the MicroCosm® Corrupt program to introduce measurement noise, GNSS range ambiguity biases, GNSS cycle slips, GNSS SV (Space Vehicle) clock errors, GNSS receiver clock errors and perturbed meteorological data.

  • Additional model errors may be introduced by perturbation of model coefficients or tabular data used when processing these data back through MicroCosm® Control and MicroCosm® Executive. Examples are perturbed station coordinates, a different gravity model or altered tabular values of Solar and Geomagnetic flux data.

MicroCosm® Sim_Soft is available as an extra cost option to the MicroCosm® POD Software and is subject to the same software license terms as the MicroCosm® POD Software.

 

MicroCosm® Site_Evo

 

The MicroCosm® Site Evolution program (Site_Evo) has been developed by Van Martin Systems, Inc. for the purpose of computing tectonic, solid Earth tide and ocean tide loading displacements of Earth satellite tracking site coordinates. Tectonic displacements are computed using either ITRF style site velocities or NUVEL style plate models. Solid Earth tide displacements are based upon the Love Number coefficient (h2), the Shida Number coefficient (l2) and the Wahr K1 tide coefficient (hk1). The ocean loading model as implemented in Site_Evo is based upon the algorithms presented in IERS TECHNICAL NOTE 21.

Site_Evo Input

Input to Site_Evo consists of seven data structures. Two of these data structures, the JPL Planetary Ephemeris DE403 and the IERS Tables File, are described in Volume 2, MicroCosm® POD File Descriptions. The other five Site_Evo data inputs include: 1) Keyword Input Control data structure; 2) NUVEL Type Tectonic Plate Model data structure; 3) ITRF Type Site Velocity data structure; 4) Site specific Ocean Loading data structure; and 5) File List data structure which relates external data file names to the Fortran logical unit numbers read by Site_Evo.

Site_Evo Outputs

Outputs from MicroCosm® Site_Evo are written to Fortran logical unit 6 and to Fortran logical unit 10. Unit 6 echoes the input and prints data subsets and other descriptive information about the functioning of Site_Evo. Unit 10 is an ASCII data file containing the displacements computed by Site_Evo. Tectonic displacements are output for a single epoch. An ephemeris of tide displacements is produced at a user specified time interval over a user specified time span.

The MicroCosm® Site_Evo Program is available as an extra cost option to the MicroCosm® POD Software and is subject to the same software license terms as the MicroCosm® POD Software.

 

MicroCosm® SLR

 

MicroCosm® SLR consists of two programs for reformatting Satellite Laser Ranging (SLR) data. These programs are MicroCosm® L2M and MicroCosm® M2G

MicroCosm® L2M

The MicroCosm® L2M program has been developed for the purpose of converting satellite laser tracking observations from "Onsite Normal Point and Engineering Quicklook" format (also known as CSTG format) into "MicroCosm Binary Tracking Data" format. Input to MicroCosm® L2M consists of a list of input observation files. In addition to two MicroCosm® Binary Tracking Data files (one for Normal Points and one for Quicklook data), a printed output file is generated which summarizes the data reformatting. The observation files output by MicroCosm® L2M may be input directly into MicroCosm® Control.

MicroCosm® M2G

The MicroCosm® M2G program has been developed for the purpose of converting satellite laser tracking observations from "MERIT-II" format into "GEODYN Binary" format. Input to MicroCosm® M2G consists of a list of input observation files. In addition to two MicroCosm® Binary Tracking Data files (one for Normal Points and one for Full Rate data), a printed output file is generated which summarizes the data reformatting. The observations output by MicroCosm® M2G must be processed through the MicroCosm® TDF before input to MicroCosm® Control.

MicroCosm® L2M and MicroCosm® M2G are available as an extra cost option to the MicroCosm® POD Software and are subject to the same software license terms as the MicroCosm® POD Software.

 


Back to MicroCosm® Home Page
webmaster@vmsi-microcosm.com