GRAIL LGRS Radio Science Experiment Data Record (RSSEDR)

RSSEDR – Radio Science Experiment Data Record

Instrument: Lunar Gravity Ranging System

PDS Data Set ID: GRAIL-L-RSS-2-EDR-V1.0DOI: 10.17189/1519558

For more information about LGRS products, see the Data Product SIS.

The Lunar Gravity Ranging System (LGRS) Radio Science Experiment Data Record (RSSEDR) data products are raw radio science data acquired at the Deep Space Network (DSN). The dataset includes DSN Doppler tracking data, open-loop data, media calibrations, and others.

Two types of measurements were obtained by the Radio Science Subsystem: closed- and open-loop recordings. The closed-loop system uses a phase-lock loop in the receiver to track the downlink signal, reporting both amplitude and frequency 1-10 times per second. In the open-loop system, the signal is simply converted to a baseband frequency range; the entire passband is sampled and recorded at 1000 or more samples per second for later processing.

The dataset includes two primary data types. Orbit Data Files (ODFs) are a product of the closed-loop system, and they are specifically targeted to spacecraft navigators and scientists interested in gravity fields. Also included are Tracking and Navigation Service Data Files (TNFs), the most primitive (and most voluminous) product of the closed-loop system. ODFs are compressed versions of TNFs. In the GRAIL context, TNFs are not considered to be a primary data type. Radio Science Receiver records (RSRs) are the primary data type from the open-loop system.

The dataset includes five secondary data types. Sky frequency (XRF) files are ASCII files with columns as follows: year, day or year, seconds past midnight, sky frequency, internal processing parameter generated in the course of creating the XFR but not relevant to GRAIL. XFR files are converted to Tracking Data Message Standard (TDM) format. TDMs are ASCII files. Biased Tracking Data Message Standard (BTM) files are generated from TDM files. BTMs are also ASCII files. For users who prefer to work with software designed for closed-loop data, TDMs and BTMs (which originate from open-loop data) are converted to the Open Loop File (OLF) and Biased Open Loop File (BOF), respectively, which are the same binary format as the closed-loop ODF.

Lastly, the dataset includes four ancillary data types for calibration. Earth Orientation Parameter Files (EOPs) are ASCII files. Ionosphere Calibration Files (IONs) provide historical and predicted Earth ionospheric conditions. Troposphere Calibration Files (TROs) provide historical and predicted Earth tropospheric conditions. DSN Weather Files (WEAs) give weather calibration information for DSN complexes. These are ASCII files of variable length records.

LGRS RSSEDR files follow a variety of file naming conventions dependent upon their type.