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Forward Link
The ISS mission forward link is similar to the forward link of EOS spacecraft that utilize the Tracking and Data Relay Satellite System (TDRSS).
For the ISS mission, elements of the forward link include a User Operations Facility (UOF) at LaRC, the Enhanced Huntsville Operations Support Center (EHOSC) at MSFC, the White Sands Ground Terminal and TDRSS. SAGE III commands will originate at the UOF and will be transmitted through the EHOSC and other ground systems to TDRSS and to the SAGE III instrument through the ISS C&DH system.
The system currently being proposed by ISS is analogous to an EOS Instrument Support Terminal (IST) with command capability. Operations timelines for forward link utilization have not been formalized at this time. The possibility of adding UOF capability within the SAGE III operations center will also be investigated.
The NASA SAGE III operations center at LaRC will develop command loads necessary to operate the instrument and transmit instrument commands via the UOF to the instrument based on schedules provided by EHOSC. Command formats will adhere to requirements of the UOF, which like the EOS IST, consists primarily of a set of software tools needed to interface with the ISS ground systems.
Return Link
Similar to the ISS forward link, the return link consists primarily of TDRSS and the EHOSC at MSFC. It is anticipated that SAGE III science data will be relayed through TDRSS to the EHOSC at least every third orbit.
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Data will be available on EHOSC computers for automatic transfer to SAGE III operations center computers. Level 0 processing will be performed by the SAGE III operations center. The EHOSC will archive raw data for at least two weeks. Like Meteor 3M operations, the SAGE III operations center will perform health, safety, and performance monitoring and will ensure that Level 0 data is transferred to the SAGE SCF and to the EOSDIS LaRC DAAC.
SAGE III housekeeping data will be available for monitoring during ISS TDRSS contacts at the LaRC UOF. The EHOSC will perform mission critical monitoring of SAGE housekeeping data and execute SAGE III provided contingency procedures in the event of a SAGE III malfunction or limit violation.
Flight Operations
SAGE III flight operations will consist of planning, execution, and analysis activities. Operations are anticipated to be more similar than different for the two identified missions and the potential FOO mission. Operations differences will arise because platform characteristics, mission unique hardware (i.e. the hexapod coarse pointing platform used on the ISS mission), and operational schedules that will vary in order to accommodate mission requirements.
Planning Activities
The basic operational plan for SAGE III operations is to obtain solar occultation data and lunar occultation data whenever the viewing geometry permits and instrument health and safety is not compromised.
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