GALAXY® and GMSEC

Summary

Galaxy® inherits from its NASA forebear, ITOS, support for GMSEC environments and standards that goes back to the inception of the GMSEC concept at GSFC.

Overview

Developers from the Hammers Company worked with the GMSEC team from the very beginning of GMSEC to establish the first set of GMSEC standard messages, and the team has maintained robust support for the GMSEC API and messages in ITOS and Galaxy ever since.  The current release of Galaxy is built and tested with version 3.7 of the GMSEC API.

Galaxy can subscribe to the bus for STOL directives, real-time and archive mnemonic value requests, and telemetry messages.  Sending STOL directives from the bus allows other GMSEC components to remotely control Galaxy.  A real-time MVAL request allows another GMSEC component to request that groups of individual telemetry values be published to a given subject on a continuous basis.  An archive mnemonic request allows another GMSEC component to request a report giving values for a set of mnemonics over a given time.

Along with receiving telemetry over TCP/IP sockets, serial interfaces, SpaceWire, and MIL-STD-1553, Galaxy can subscribe to telemetry transfer frames and/or packets over the GMSEC  bus.  This capability allows the system to receive data from a GMSEC-compliant ground station or front-end processor, or any other GMSEC-compliant telemetry source.

Galaxy can publish heartbeats, log messages, telecommands, and telemetry to the GMSEC bus.  Heartbeats provide confirmation that Galaxy is up and performing nominally.  Publishing log messages allows Galaxy’s detailed status and progress to be aggregated with log messages from other GMSEC-compliant tools, and to be monitored by GMSEC tools for significant events or anomalies.  Telecommand requests are sent over the bus to convey telecommands to other GMSEC entities, maybe including ground station equipment.

Galaxy can publish to the bus telemetry frames and/or packets that it receives over other interfaces so as to make the telemetry available to other GMSEC-compliant tools.  In response to an MVAL request over the GMSEC bus, Galaxy also can publish to the requested subject groups of telemetry values.  MVAL messages are published whenever new values are received by Galaxy, and for each mnemonic value sample they contain a time stamp, raw value, converted value, status, and flags (including quality and limit violation flags).

Details

Galaxy provides the following applications for participating in a GMSEC environment:

gmrequestDirective Request Message Publisher

This program takes a subject name and text directive over a TCP socket and publishes is to the given subject.

gmsubscribeDirective Request Message Subscriber

This program subscribes to a given subject and sends any messages received to the ITOS STOL interpreter.

gmdatavalReal-Time Mnemonic Value Request Subscriber

This program subscribes to a given subject on which it expects to receive mnemonic value request messages (MVAL REQ).  Upon receiving a request, the program responds with initial data values, and configures itself to continuously publish values for the mnemonics given in the request on the subject given in the request.  The program can accept and service an unlimited number of requests.

gmreqvalReal-Time Mnemonic Value Request Publisher

This program sends out a mnemonic value request message (MVAL REQ).

gmarchvalArchive Mnemonic Value Request Subscriber

This programs subscribes to the given subject for archived mnemonic value requests, which contain a list of telemetry mnemonics and a time range.  In response to this request, the program generates a tabular report containing all values for the given mnemonics over the given time range.  It replies to the request with either the report itself or a URL where the report can be retrieved, depending on which was requested.

gmmessage – Heartbeat Message Publisher

This program publishes a heartbeat on the GMSEC bus.

gmpublogLog Message Publisher

This program publishes to the given subject all Galaxy log messages (except debug messages).

gmsendfrmReal-Time Telemetry Data Message Frame Publisher

This program publishes to the given subject CCSDS telemetry transfer frames received over a TCP socket connection.  An included Galaxy STOL procedure launches the application and arranges for telemetry to be provided to it.

gmsendpktReal-Time Telemetry Data Message Packet Publisher

This program publishes to the given subject CCSDS telemetry space packets received over a TCP socket connection.  An included Galaxy STOL procedure launches the application and arranges for telemetry to be provided to it.

gmtelemReal-Time Telemetry Data Message Subscriber, Frames and Packets

This program subscribes to the given subject to received CCSDS telemetry transfer frames or space packets over the bus, and forwards what it receives to the Galaxy telemetry subsystem for processing.

gmsendcmdReal-Time Sending of Command Frames and Packets

This programs publishes to the given subject CCSDS telecommand transfer frames or space packets.  It receives frames or packets from the ITOS command subsystem over a TCP socket.

gmrcvcmdReal-Time Receiving of Command Frames and Packets

This program subscribes to the given subject and expects to receive telecommands over the bus.  Received commands are output over a TCP socket (to the ITOS command subsystem).

gmdebugCapture and output GMSEC Messages

This program subscribes to the given subject and writes any messages received to standard output.

Conclusion

Galaxy support all of the essential GMSEC interfaces needed for it to play the key role of mission telemetry and command system for any project planning to use the GMSEC bus and message standards in its mission operations center design.  The Galaxy team has supported GMSEC from its inception, and plan to maintain and expand that support into the future.