Fundamental Technologies

Galileo Spacecraft Pages

Galileo EPD Command Density at Satellite Encounter

Source: R. C. Moore, March 6, 1979

Ed Nipper, the JPL EEIS uplink coordinator, has requested that the EPD command density be estimated for satellite encounter situations.  The primary concerns are:

  1. How many different ground data command types are liable to be used at encounter, and
  2. How frequently will ground data commands have to be sent to the EPD at encounter.

Because much of the EPD operation is controlled by the internal microprocessors, the command density should be very low at all times, even at satellite encounters. We estimate that our maximum rate for ground data commands shall not exceed one data command per minute.

The following list shows the various data commands which might be sent during satellite encounter:

MNEMONICOP-CODEDESCRIPTION
EPD RESCAN01Resume scanning
EPD ASCANB16Enter accelerated scan mode
EPD ASCANF17Exit accelerated scan mode
EPD LEMSOF80Turn off LEMMS
EPD CMSOFF91Turn off CMS
EPD LEMSONA0Turn on LEMMS
EPD CMSONNB1Turn on CMS
EPD GOTOS018Go to sector 0
EPD GOTOS119Go to sector 1
EPD GOTOS21AGo to sector 2
EPD GOTOS31BGo to sector 3
EPD GOTOS41CGo to sector 4
EPD GOTOS51DGo to sector 5
EPD GOTOS61EGo to sector 6
EPD GOTOS71FGo to sector 7
EPD ENAALTC4Enable CMS alternate J/J'mode
EPD DISALTC5DIsable CMS alternate J/J'mode
EPD TLMFM1D0Select EPD TLM format #1

The EPD requires no periodic data commands.

Next: Servicing the Galileo EPD Rate Channel Accumulators

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Updated 12/10/04, T. Hunt-Ward
tizby@ftecs.com