We plan a limited set of observations for instrument checkout and calibration following instrument turn-on on the approach to each solar encounter. A few images per day will be taken for up to ten days while the spacecraft distance from the Sun is less than 0.5 AU on the inbound segment of each orbit. Some of these images may involve small off-points of the spacecraft from the Sun (up to a few arc minutes) to verify the stray light performance of the instrument.
Routine observations to meet the science objectives occur during a window of ∼10 days duration centered on perihelion when the spacecraft is within 0.25 AU of the Sun (see Table 6).
The WISPR Flight Software (FSW) is developed by the APL IDPU team. It incorporates considerable heritage/commonality from other missions such as MESSENGER, MRO/CRISM, New Horizons, and Solar Orbiter/SIS. The common software makes use of heritage boot code, telemetry and command packet handling, macro (stored command script) implementation, memory management, autonomy, and reporting modules. The data interface with the spacecraft is SpaceWire and has a SPP-specific protocol with static bus schedule and Instrument Transfer Frames.
NASA categorizes Data Products based on a system of Levels starting with Level zero. A level zero data product is usually defined as representing raw, but cleaned spacecraft telemetry. Subsequent data levels represent successive levels of data processing involving calibration and the application of science algorithms. The SPP mission has defined five data levels that are described elsewhere.
The detailed observing schedule will be uploaded prior to the beginning of each perihelion pass. However, there may not be sufficient time to modify the detailed schedule for the upcoming perihelion passage after the download of the SRR from the preceding pass. For this reason, the observing objectives are defined for the next two perihelia.
Documentation necessary for data analysis and interpretation will be made available through the WISPR website. These will include:
- Instrument description.
- Calibration and Validation methodology.
- Validation through cross-calibration with other instruments or other assets (if applicable).
- Dataset description including FITS header definition.
- Meta-data products.
The radiometric calibration of the data will be performed using the pre-flight laboratory calibration data and calibration updates using observations of an ensemble of stable stars as used for SOHO/LASCO and STEREO/SECCHI. The calibration team monitors the detector telemetry and the images and provides periodic updates to the science calibration routines. IDL procedures will be provided in the Solarsoft library to convert the Level-1 FITS image files into higher-level calibrated data products.