Wilkinson Microwave Anisotropy Probe

Product Name
Telemetry Data


The final WMAP data release includes a much larger collection of telemetry data than has been supplied in the past. WMAP data was trasmitted from the satellite in NASA's CCSDS format; each day of data was split into four files prior to delivery to the science team:

INHKInstrument housekeeping
OBHKSpacecraft (or observatory) housekeeping
INHKExtended spacecraft housekeeping
INSCScience data

The housekeeping data consists of many different packets fo data; each packet is identified with an application identifier (or apid). Each packet has a time stamp associated with it and contains multiple data points, each identified by a unique mnemonic. Several 'pseudotelemetry' packets were also defined; the mnemonics from these 'packets' are computed from data extracted out of multiple telemetry packets.

The CCSDS format is no longer used by NASA missions, having been replaced with a new format. Therefore, to spare the user from having to parse out the contents of these files and then converting this data from the original form into something more useful (counts to volts, for example), selected measurements from these files have been rewritten into a single FITS file for each day.

Each FITS file contains 58 binary FITS tables. The first five tables contain the science data, one table for each differencing assembly. Many of the rest of these tables contain data from a single apid/packet. The rest are one or more pseudotelemetry mnemonics that share the same timestamps. The underlying feature of all the data within a given table is that contents of each row in the table share the same time. Within each binary table, the first column contains a time in WMAP Reduced Julian day (Julian day less 2,450,000; this allows precision to the submillisecond level); a column follows for each mnemonic. The header contains a brief description of each mnemonic.

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A service of the HEASARC and of the Astrophysics Science Division at NASA/GSFC
Goddard Space Flight Center, National Aeronautics and Space Administration
HEASARC Director: Dr. Alan P. Smale
LAMBDA Director: Dr. Eric R. Switzer
NASA Official: Dr. Eric R. Switzer
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