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The Galileo Energetic Particles Detector


Galileo EPD Handbook




Appendix C. Magnetometer Subsystem


Table of Contents:



Source: Document 625-610, revision dated 2/16/83


The MAG EDR science record is designed to a RIM cycle containing 91 minor frames. Each minor frame corresponds to a MOD 91 count.  The Mag record shall be placed onto the MAG science EDR along with AACS records in time order.  The logical record structure is diagrammed in Figure 1.


Figure 1. MAG Record.


Standard Header
(17 32-bit words)
Standard Subheader
(54 32-bit words)
MAG Data
(455 32-bit words)


Processing Start/Stop. Refer to Subsection 5.2*  (see below).


Record Buildup. Mag science record buildup shall proceed with the extraction from the appropriate bit locations from minor frames 1 through 91 of each RIM cycle. Subsection 5.2* defines the basic data extraction procedure.


Record Header. The MAG record shall receive a standard record header (refer to Section 4). (Ed. note: Section 4 is incorporated into this handbook as Appendix B, SEDR Files.)


Record Subheader. The MAG subheader contains a standard subheader which contains selected engineering measurements in DN extracted from the engineering packet of the LRS data block (channels from the fixed engineering data). Refer to Figure 5-1 on page 5-3 (figure incorporated below).


Standard Subheader Format:



Data Block. The MAG data block contains data extracted from bits 2880 through bits 3039 of each minor frame from the golay compressed LRS data block of the input SDR record. Specified word locations shall be maintained within the data block. Refer to Figure 2 below for data block format and GLL-3-280 Appendix A (not available on this website) for detailed definition of the data fields.


Figure 2. MAG Data Block Format



*Subsection 5.2:


EDRGEN shall extract the AACS, science and science-related engineering channels for each LRS minor frame. EDRGEN shall then build individual experiment records and AACS records by combining all minor frames corresponding to a RIM cycle (91 minor frame) placing the start time of the first minor frame into the record header and appending SCET, golay correction flags and data presence indicator flags as indicated in Section 4. An accumulation of summary data shall be performed with the summary of each EDR tape being provided.


EDRGEN shall extract data from the LRS frames using the spacecraft clock (SCLK) count to control the extraction process. The following criteria are to be applied to SCLK count for each LRS minor frame:


  1. When the SCLK count increments by a value equal to a minor frame (MOD91 count), the program will continue building the current major frame (corresponds to a RIM count).
  2. When the SCLK is greater that one MOD91 count, but in the same RIM count, the program will locate the data by minor frame location within the record and update the current major frame, flagging filler blocks as appropriate.
  3. When the SCLK count equals or is less than the previous SCLK count, the program shall flag the remainder of the current major frame as containing filler, output the major frame, and begin updating a new major frame with the current major frame, flagging filler blocks as appropriate.
  4. When the SCLK count increments the RIM count, the program will output the current major frame, flagging filler blocks as necessary. The program will then begin constructing a new major frame with the current minor frame, flagging filler blocks as necessary.
  5. When any LRS frame, from which data is extracted, contains filler, the extraction function will flag the affected minor frame within the record as containing filler.



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Updated 8/23/19, Cameron Crane


Manufacturer: The Galileo Spacecraft was manufactured by the Jet Propulsion Laboratory, Messerschmitt-Bölkow-Blohm, General Electric, and the Hughes Aircraft Company.

Mission Duration: Galileo was planned to have a mission duration of around 8 years, but was kept in operation for 13 years, 11 months, and 3 days, until it was destroyed in a controlled impact with Jupiter on September 21, 2003.

Destination: Galileo's destination was Jupiter and its moons, which it orbitted for 7 years, 9 months, and 13 days.