CRD Format Overview

Version V1.01

Due to technology changes, the International Laser Ranging Service (ILRS) formats for exchange of laser full-rate, sampled engineering and normal point data were replaced a number of years ago. The main technology drivers were the increased use of kilohertz firing rate lasers which made the full-rate data format cumbersome, and anticipated transponder missions, especially the Lunar Reconnaissance Orbiter (LRO), for which various field sizes are either too small or nonexistent. Rather than patching the existing format, a new flexible format encompassing the 3 data types and anticipated target types was created.

The purpose of the Consolidated Laser Ranging Data Format (CRD) is to provide a flexible, extensible format for the ILRS full-rate, sampled engineering, and normal point data. This format is based on the same features found in the ILRS Consolidated Prediction Format (CPF), including separate header and data record types assembled in a building block fashion as required for a particular target. There are 3 separate sections to the data format: 1) the header section which contains data on the such topics as station, target, and start time; 2) the configuration section containing an expanded version of data previously described by the System Configuration Indicator (SCI) and System CHange indicator (SCH) fields; and 3) the data section containing laser transmit and receive times, and other highly dynamic information. The data headers in version 1 are fixed format and similar in content to those of the CPF files. The configuration and data records are free format with spaces between entries. Records can be added as needed for the specific data types and at frequencies commensurate with the data rate. For example, at a 2 kHz ranging rate, meteorological data and pointing angles are commonly read far less frequently than the ranges. Note that 1 way outbound, 1 way inbound, and 2 way ranges can all appear within one file. Also note that multiple color ranging data can appear in one file.

Features of this format are as follows:

  • Flexibility. The data files can be simple and compact for kiloHertz ranging or comprehensive for more complex data structures, as appropriate.
  • The building block structure with multiple record type allows for including and omitting certain
    records types as needed by a station or target.
  • Configuration descriptions are addressed in a more explicit, logical and extensible manner than the current format.
  • A single integrated format can be used for current and future data and target types.
  • Multiple color data, multiple ranging modes (transponder one and two-way ranges) and multiple configurations can be included naturally within a single data file.
  • The format can be expanded in the future as needs expand without abandoning the entire format.
  • All data types (full rate, sampled engineering, and normal point) can be managed in a single file if desired, e.g., for archival and reference purposes.
  • Fields in the Configuration sections are compatible with the SLR Engineering Data File (EDF)
    format.

Data from a subset of the ILRS network sites are available and accessible at the CDDIS:

and at the EDC:

CRD sample code (also created by Randy Ricklefs) is available. An errata page (last updated 28-Dec-2017) has been created to annotate changes to/problems in the documentation and source code.

Personnel at EDC have developed a procedure to test CRD files. This capability will help SLR station staff in checking their generated CRD files for format and content. It provides a rigorous check of the format and the content of CRD files. The software is available at:: http://129.187.165.2/typo3_crd. Users must register; EDC will then create and activate the account.

Version 2.01

The first significant revision of the format since the initial installations in 2008 is now being finalized. A header record has been added to specify the predictions used to track the target, and configuration records for software versions and meteorological sensors have also been added. A calibration detail record has been added to provide pre- and post-calibration results. The header records are now (like the configuration and data record) also free format. Many of the other changes are small improvements of the formats, which come from various sources. As with CPF v2, the target type has been split into target class and location. Some earlier blunders have been fixed, and the language has been made more general for those not familiar with the ILRS nomenclature. Appendix C of the format document provides allowable values for each of the data fields (does not currently include the new v2 fields). Appendix D explains the considerations and changes that went into CRD v2. The format manual can be found here, and the sample code can be found here. A basic set of v2-compliant CRD normal point files can be found here. A v2 errata page has been created to annotate changes to/problems in the documentation and source code.

Data from the ILRS network sites are available and accessible at the CDDIS:

and at the EDC:

Related information: