Figure 1.2: SOHO ground system: basic functions related to science operations
The diagram in Fig 1.2 shows the basic functions that will be present for the SOHO science operations. The SOHO Experiment Operations Facility (EOF), to be located at NASA Goddard Space Flight Center, will serve as the focal point for mission science planning and instrument operations. At the EOF, experiment PI representatives will receive real-time and playback flight telemetry data, process these data to determine instrument commands, and send commands to their instruments, both in near real-time and on a delayed execution basis. They will be able to perform data reduction and analysis, and have capabilities for data storage. To accomplish these ends, the appropriate experiment teams will use workstations (WS's) that will be connected to an EOF Local Area Network (LAN). Additional workstations and X-terminals will be used to support the Project Scientists (PS) and for SOHO planning and operations support staff in the EOF. There will be connections from the EOF to external facilities to allow transfer of incoming data from GSFC support elements, remote investigator institutes, other solar observatories, and ESA facilities. There will also be connections for the EOF to interact with the SOHO Mission Operations Control Center (SMOCC) and other required elements at GSFC for scheduling and commanding the SOHO flight experiments. Short term and long term data storage will be either within the EOF or at an external facility with electronic communication access from the EOF.
The Deep Space Network (DSN) will receive S/C telemetry during three short (1.6 hrs) and one long (8 hrs) station pass per day. Science data acquisition during non-station pass periods will be stored on-board and played back during the short station passes. The MDI high data rate stream will be transmitted only during the long station pass. For 2 consecutive months per year continuous data transmission, including MDI high data rate, will be supported by DSN. Whenever there is data transmission, the basic science data (40 kbits/s) and housekeepig data (15 kbit/s) will be available in near real-time at the EOF. From the EOF the SOHO investigators will control the operation of the instruments via the Payload Operations Control Center (POCC). The latter will verify and up-link the commands submitted by the experimenters.
Some SOHO instruments (CEPAC, CELIAS, VIRGO, GOLF, and SWAN) will generally operate automatically and will not need near real-time operational control except for surveillance of housekeeping data. Other instruments, those of the coronal imaging investigators, will be operated interactively every day in real (or near real-) time.
The EOF has the following functions: