NGIMS Mission Ops and Commanding Meeting
APL
Dec 28, 2000

Present:
Mark Holdridge
Carl Wittenburg
Wayne Kasprzak
Paul Mahaffy
Mike Paulkovich
Eric Raaen
Florence Tan

Goal: discuss Spacecraft/NGIMS commanding details.

Result: Commands can be also transmitted in real time using STOL or scheduled as part of a SEQGEN (short for Sequence Generator) upload. NGIMS will use SEQGEN as the tool to create and schedule commands for the CONTOUR C & DH.

Details:
Two ways to command instruments:
1) STOL (Spacecraft Test and Operations Language). STOL is used to for one-time only, real-time commands eg pyros, pressure test, patches.
2) SEQGEN. SEQGEN commands are pre-made, pre-tested, and are sequenced as part of general command sequencing on spacecraft e.g. baseline, TCA 
sequence.

During I & T, all commanding done via STOL.
During Mission Ops Sims,all commanding will be done via SEQGEN. We agree to command NGIMS via SEQGEN SSF files during the mission.

SEQGEN is a JPL tool that sequences spacecraft commands. Commands are sequenced and then simulated to track power usage, illegal commands based on predetermined flight rules, command conflicts etc. From the point of view NGIMS, we will submit command/fragment/CAS(Canned Activity Sequences)  mnemonics to the sequence generator (Ann Harch?). SEQGEN needs an SASF input file to generate the SSF output file. We will provide the time and mnemonics for the sequence generator to generate the SASF file. The SASF file will be translated into an SSF by the SEQGEN system. The SSF outputs an ASCII text file with every command in time order and time-stamped. The SSF file is then translated into binary format and uploaded to C & DH.

Definitions:
Commands - instructions to the instrument. Commands can have fixed, default or variable parameters.
Fragments - a logical list of command mnemonics. ASCII text with format based on command dictionary. Commands in fragments can be separated by absolute or relative times. Eg: Open source unity scan. Fragments should be constructed with reusability, versatility in mind. They should also be made so that they "stand-alone" and can be invoked independently of other fragments.
CAS (canned activity sequence) - CAS' call fragments. example: baseline Requests - a list of CAS'.
SASF - a list of requests. It can include requests from other instruments.

SEQGEN Access:
APL requests that we log in remotely. They prefer to maintain only one database for the entire spacecraft. Cornell is designated SEQGEN site.

SEQGEN System Requirements:
Sun Solaris OS 2.8
Sun Ultra 10 (?)

Personnel requirements:
1 Prime Sequencer
1 Backup Sequencer
1 Prime Instrument Engineer
1 Back up Instrument Engineer

Instrument Engineer will sign off on all CAS and Fragments or Sequences.

Patches:
Done using STOL and SEQGEN generated SSF. This is so that if one fails, we can use the other. Patch loads will be followed up with a dump and a compare.

Velocity Issues:
APL will target flyby system ("thread the needle") without worrying about the time of flyby or time of closest approach (TCA) and the velocity. However, APL assures us that the CA velocity should be known at launch. There is not enough propellant to change velocity by a large margin.

Closest Approach Sequence:
Any changes to TCA sequence will be uploaded via table patches with variables as its data parameters. Last absolute time to upload a change is about 2 days from TCA. This upload will be performed using STOL.

Inputs to Goddard and Ryan Miller:
SASF format and pertinent SEQGEN format
SSF format
Binary format
STOL format