Helix Nebula Banner Image

The Galileo Energetic Particles Detector


Galileo EPD Handbook


Chapter 2. EPD Software


EPD SBAND Mission Software Requirements (continued)

Source: S. Jaskulek, various dates


EPD Rate Channel Data Processing



Table 3. EPD Rate Channel Packet


Byte # Description
1 b0: Update flag (MSB)
    1: new; 0:old
b1, b2: Spin quadrant
    00:A; 01:B; 10:C; 11:D
b3: New spin
    0:same; 1:new
b4: Map ID
    0=MAP1; 1=Map2
b5-b7: Motor position (LSB)
    000:Pos.0;...111:Pos. 7
2, 3, 4 Rate Channel 1 (24 bits)
5, 6, 7 Rate Channel 1 (24 bits)
8, 9, 10 Rate Channel 3 (24 bits)
... ...
143, 144, 145 Rate Channel 48 (24 bits)
146 HV Monitor Value
147-151 Housekeeping/Status
152-211 12 PHA events (20 bits each) and 30 bytes of filler, or
24 PHA events (20 bits each


Once the data is retrieved by the CDS, it must sequentially go through the 24-bit rate channel values and add them to the proper rate channel bins defined in the CDS memory.  The addition algorithm for this may be fairly simple (see Appendix A for more details, but determining which bin to address is not so straightforward. This task will be addressed in section 7.


The motor position, spin quadrant, and motor direction (in the science record status byte), all represent the values present during the quadrant that was just completed.  In other words, the motor and spin parameters match up with the rate channel data that is also present in the data for that minor frame.  One could expect, therefore, that in a minor frame data packet in which the "new spin flag" is set, the spin quadrant will equal "D."



Next: Telemetry Output Buffers in the EPD Memory 


Return to Galileo EPD Handbook Table of Contents Page.

Return to main Galileo Table of Contents Page.
Return to 
Fundamental Technologies Home Page.


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.