Following the successful dynamic planning and implementation of IRAC Warm Instrument Characterization activities,
transition to Spitzer Warm Mission operations has gone smoothly. Operation teams procedures and processes required
minimal adaptation and the overall composition of the Mission Operation System retained the same functionality it had
during the Cryogenic Mission. While the warm mission scheduling has been simplified because all observations are
now being made with a single instrument, several other differences have increased the complexity. The bulk of the
observations executed to date have been from ten large Exploration Science programs that, combined, have more
complex constraints, more observing requests, and more exo-planet observations with durations of up to 145 hours.
Communication with the observatory is also becoming more challenging as the Spitzer DSN antenna allocations have
been reduced from two tracking passes per day to a single pass impacting both uplink and downlink activities. While
IRAC is now operating with only two channels, the data collection rate is roughly 60% of the four-channel rate leaving a
somewhat higher average volume collected between the less frequent passes. Also, the maximum downlink data rate is
decreasing as the distance to Spitzer increases requiring longer passes. Nevertheless, with well over 90% of the time
spent on science observations, efficiency has equaled or exceeded that achieved during the cryogenic mission.
The Spitzer Space Telescope launched in August 2003, and has been in its nominal operations phase since December
2003. This paper will review some of the pre-launch, high-level project requirements in light of our operations
experience. We discuss how we addressed some of those requirements pre-launch, what post-launch development we've
done based on our experience, and some recommendations for future missions. Some of the requirements we examine in
this paper are related to observational efficiency, completeness of data return, on-board storage of science data, and
response time for targets of opportunity and data accountability. We also discuss the bearing that mission constraints
have had on our solutions. These constraints include Spitzer's heliocentric orbit and resulting declining telecom
performance, CPU utilization, relatively high data rate for a deep space mission, and use of both on-board RF power
amplifiers, among others.
This paper explores the how's and why's of the Spitzer Mission Operations System's (MOS) success, efficiency, and affordability in comparison to other observatory-class missions. MOS exploits today's flight, ground, and operations capabilities, embraces automation, and balances both risk and cost. With operational efficiency as the primary goal, MOS maintains a strong control process by translating lessons learned into efficiency improvements, thereby enabling the MOS processes, teams, and procedures to rapidly evolve from concept (through thorough validation) into in-flight implementation. Operational teaming, planning, and execution are designed to enable re-use. Mission changes, unforeseen events, and continuous improvement have often times forced us to learn to fly anew. Collaborative spacecraft operations and remote science and instrument teams have become well integrated, and worked together to improve and optimize each human, machine, and software-system element. Adaptation to tighter spacecraft margins has facilitated continuous operational improvements via automated and autonomous software coupled with improved human analysis. Based upon what we now know and what we need to improve, adapt, or fix, the projected mission lifetime continues to grow - as does the opportunity for numerous scientific discoveries.
The Cassini Science Operations and Planning Computers (SOPC) are meant to give Cassini investigators and the Huygens Probe Operations Center (HPOC) more direct control of and responsibility for their instruments and their data and to reduce mission operations cost. SOPCs give the investigators the ability to command their instrument directly, but also the responsibility to do so correctly. The SOPCs help reduce mission operations cost by allowing the instrument designers also to be the operators. The SOPCs allow the operators to participate directly even though they are at a distance from JPL. The SOPCs are direct extensions of the Cassini Ground System to the investigator's home institution. They provide links to the rest of the Cassini Ground System for both uplink and downlink functions. The SOPCs use the same software as the rest of the ground data system. They also provide a platform for project and investigator provided planning and analysis tools. The current SOPC design is targeted toward Cassini Assembly Test and Launch Operations and cruise. Improvements planned during cruise include hardware upgrades, changes in software architecture, changes to the data communication systems and enhanced security features. The SOPCs, without proper precautions, could pose a security liability. The philosophy of the security requirements and some particular measures will be discussed.
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