MESSENGER RSS Ionosphere (media) Calibration Record (ION4)

ION4 – PDS4 Ionosphere (media) Calibration Record

Instrument: MESSENGER Radio Science Experiment

PDS4 Bundle: urn:nasa:pds:mess-rs-rawDOI: 10.17189/tcy9-gv38

For more information about RSS ION products, see the TRK-2-23 Product SIS.

The Radio Science Subsystem (RSS) Ionosphere (media) Calibration Record (ION4) files are Deep Space Network (DSN) TRK-2-23 Media Calibration files. These provide ionospheric calibration information. They are of two types, Doppler and range data and Delta Differenced One-way Ranging (VLBI).

The distribution of charged particles in the ionosphere is highly inhomogeneous. The magnitude of the ionospheric range delay at a given site depends on the spacecraft line-of-sight and on the observing frequency, time of day, season, and time since the start of the current solar cycle. At S-band, the zenith ionospheric delay ranges from less than 1 meter to more than 10 meters, and the delay at 0 degrees elevation is about 3.5 times as large.

Ionospheric calibrations are given by a normalized polynomial for each tracking pass at each Deep Space Communications Complex (DSCC) or Deep Space Station (DSS). The time span of the calibration is from spacecraft rise (0 degrees) to set (0 degrees) at the receiving station or complex. The calibration represents the one-way ionospheric range delay to the spacecraft, in meters at a nominal S-band frequency of 2295 MHz. The Orbit Determination Program (ODP) adjusts the calibration to the tracking frequency that is used.

A comment before each calibration indicates the post-fit residual of the fitted polynomial, in meters at S-band. A comment at the end of each calibration indicates the date and time it was created and the source of the data used.

RSS ION4 products have the following file names:

MESS_RS_yyyyddd_eee_tt_ION.TXT (with detached PDS label)

where:

MESS = MESSENGER mission

RS = Radio Science Subsystem

yyyy = the ION data start year

ddd = the start day of year

eee = the stop day of year (which may be in the next year)

tt = file type

VL = the file is to be used with VLBI (DDOR) data

DP = the file contains calibration data for Doppler measurements

ION = the product type is Ionospheric (media) calibration

In ODE, ION4 products have the following product IDs:

mess_rs_yyyyddd_ddd_tt_ion