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Data sets

  The purpose of this section is to describe the data sets available in the EOF and at the different SOHO facilities.

Science data

NASA will forward real-time level 0 (=packetized) science data from the GDCF/Pacor (Generic Data Capture Facility/Packet Processor) to the EOF Core System, which will distribute it to the PI Workstations. There is no additional front-end processing performed on these data by NASA to assess the quality prior to its routing to the EOF. Playback data will be sent to the EOF in the same manner with transmission delays from DSN (approximately 3 hours) and processing delays to turn the data around (approximately 2 hours).

Housekeeping data

NASA will provide the level 0 housekeeping data packets obtained from the raw telemetry stream. These data are treated the same way as the science data. The SMOCC will provide the EOF with access to the SMOCC displays. The displayed data will be available in both raw counts and engineering units, and will include housekeeping parameters defined in the Project Data Base.

Ancillary data

Various parameters relating to the spacecraft condition will be collected together into a data set called ancillary data. Table 3.1 provides a list of the parameters that are to be included in the ancillary data set. The data set may be accessed electronically from the EOF and will be maintained for the entire SOHO mission. Some of the ancillary data parameters will be transmitted to the DDF for distribution on hard media to the PIs.

All the parameters, except for the verified attitude, will be generated by SMOCC or FDF. The verified attitude will be the responsibility of the PI teams, and will be generated from a comparison of the definitive attitude with science data. The verification process is anticipated to be a long-term process and will therefore not be included with the ancillary data set distributed by the DDF.

The Definitive Attitude file now consists of two products, (a) the Definitive Attitude File and (b) the Full Time Resolution Attitude File.

It is anticipated that the on-board clock may occasionally jump. Therefore corrections to the on-board clock must be accommodated and the list of ``glitches'' be maintained on-line and distributed by the DDF. The frequency corrections to keep the clock within 20ms will be logged, too.

Table 3.1: Ancillary data parameter

Summary data

  The Summary Data will be used both to plan observations at the EOF and to provide an overview of the observations that have been obtained from the SOHO. Tables 3.2, 3.3, and 3.4 provide a list of the contributions from each PI team. The Summary Data will consist of three classes. The first two classes will consist of a representative image from each of the imaging experiments, and key parameters from the non-imaging experiments. The third class will be a list of observing programs and start/stop times of data sequences. Together these data will provide a synopsis of solar conditions and the science programs that have been carried out by the observatory.

The Summary Data will be available on-line from the EOF for 28 days and will be transmitted to the DDF for distribution on hard media to the PIs. Tables 3.2, 3.3, and 3.4 also include an estimate of the daily storage requirement. The total requirement is determined essentially by the number and size of the images, and is 20Mbyte/day. If it is necessary to reduce this requirement, smaller and/or 1 Mbyte images can be considered.

The Summary Data will be the responsibility of the PI teams, and are to be generated as quickly as possible after receipt at the EOF. The data will be generated from quick-look science data and will have only preliminary calibrations performed on them. The Summary Data will therefore NOT be citable. The individual PI summaries will be transmitted by the PI to the Science Operations Coordinator's workstation (or other appropriate disk file system) either by file transfer (e.g. ftp) or by electronic mail.

An event log will be maintained in the summary data file and will be distributed by the DDF. However, the contents of the log at the EOF will be allowed to change, and will therefore be different than the one distributed by the DDF. The event log will provide a registry of events that may be of general interest. The log may also include events identified by observatories other than SOHO, but which might be relevant to the SOHO observations.

Table 3.2: Summary Data File I: Images (size per day)

Table 3.3: Summary Data File II: Parameters (size per day)

Table 3.4: Summary Data File III: Observation programmes (size per day)

  1. Each of the instruments will have an observation program summary data file even if they have only a few entries.
  2. The observation program will have both a planned and an executed data file. Ideally the formats of the planned and executed files should be identical. In addition, it would speed up generation of the executed data file if it could be extracted entirely from the command history log (instead of from the instrument data streams).
  3. A standard format for the observation program file will be defined for all the instruments in order to make it easier to correlate observations. The format could include Operation Mode, Start Time, Stop Time, and Observing Parameters. The Operation Mode would include instrument name, detector, and observing sequence identification. The Start and Stop Times would be in a well defined format (for example, yymmdd The Observing Parameters could include heliographic area covered, field of view, sequence number, events, etc. and might have the format of parameter=value.
  4. The observation program might be better as a database apart form the summary data. In addition, it would be a good place to start with the definition of a catalog and keywords. The disadvantage of having the observation program as a stand-alone database would be the difficulty of updating the information. This would be less of a problem if the observation program database could be generated automatically from the command history log.

Processed science data

Each investigation group will convert the level-0 Science data and other related data into more elaborate data files (or have the necessary software) for scientific analysis. Any processed data must have a level greater than 0 (i.e. level 1,2, etc...). Details of the archived files are to be found in the individual experiment Operations Manual. Table 3.5 gives an indication of the files to be generated.

Table 3.5: Processed science data

Synoptic information and predictive information

The following data sets will be available at the EOF by electronic means either from SELDADS or directly from solar ground-based observatories. Among the ``core support observatories'' are Mitaka, Nobeyama, Norikura (all Japan), Huairou (China), Ondrejov (Czech Republic), Pic du Midi (France), Izana (Tenerife), Huntsville, SEL (Boulder), Sac Peak, Kitt Peak, Big Bear, Mt.Wilson, Mees, and Mauna Loa (all USA).

Provided data from ground stations are:

Provided data from other S/C:

Provision to other projects from SOHO:

next up previous contents
Next: Dissemination and archiving Up: Data Previous: Data

SOHO Archive
Fri Apr 28 14:32:42 EDT 1995