This article describes the major differences between products produced by the FIMS team and products produced by the SPEAR team.
For detailed descriptions of these products, see instead File Names and Content. For an overview of the FIMS and SPEAR teams, see Mission Teams. For a more detailed accounting of how some of these differences derive from the product pipeline, see Data Processing. For data access, see Data Access.
FIMS and SPEAR are two mission teams that worked on the same telemetry stream (and the exact same instrument) to produce different products. This table is a non-exhaustive chart of differences between the output of the FIMS vs. SPEAR product pipelines, to be used as a preliminary guide for users deciding which product to use. We encourage users to consider testing out products from both teams, to examine how these differences play out for your particular science case.
The table is color-coded light-blue/white, in which light-blue represents "advanced" features of a data product. Please note that products with "advanced" features are not necessarily more scientifically accurate or better suited to your particular science case. Rather, they may represent an extra degree of work that the team put into the feature (as in the case of the FIMS team's attitude correction procedure to recover photons with time-delayed attitude reporting, or the case of the SPEAR team's two-step star removal procedure to remove starlight without leaving large holes), the degree of detail in the data (as in the case of spatial resolution), or the availability of data.
| Feature | FIMS | SPEAR |
|---|---|---|
| Spatial resolution of hyperspectral maps | Higher resolution down to 7 arcmin | Lower resolution down to 27.5 arcmin (L band) or 55 arcmin (S band) |
| Spatial binning of integrated emission line maps | Adaptive smoothing down to 55 arcmin. | Adaptive binning down to 13.7 arcmin (for all lines except O III). |
| Available emission line map species | C IV, O VI, and H2 only. | C IV, O VI, H2, Al II, C II, C III, He II, Lyman Beta, N II, O I, O IV, Si II, Si IV, and low-resolution OIII. |
| Photons with time-delayed attitude reporting | Repaired with Attitude Correction, recovering most orbits | Removed up to about 20% of the total number of orbits used in the FIMS pipeline |
| Effective areas | Time-dependent effective area vs. wavelength curve (see Effective Area | Grasp), accounting for the severe decline in S-band sensitivity over time | A single grasp vs. wavelength curve was used for all data (identical across all temporal and spatial bins) |
| Star removal procedure | Star Removal was applied to the 7 arcmin-resolution HEALPixel maps | Two-step star Star Removal procedure which first worked directly on the telemetry stream to remove star photons before applying a filter to the 13.7 arcmin-resolution HEALPixel maps, resulting in the removal of fewer sky pixels |
| Hyperspectral maps without stars removed | Hyperspectral maps both with and without stars removed are provided for all combinations. Stars have been removed from emission line maps. | Stars are removed from all products |
| Shutter mode apertures included in hyperspectral maps | 100%, 10%, and merged 100%+10% for hyperspectral maps. However, the FIMS team recommends that users default to the 100%-only data. | 100% only |
| Celestial coordinate system (can be transformed, but not without smoothing from interpolation between pixels) | Galactic | Ecliptic |
| Sky coverage | Includes extra coverage in a medium-sized area of the southern Galactic hemisphere, but this area has low signal-to-noise. The reason for this difference is under investigation. | Includes some extra coverage in small regions (calibration sweeps on bright stars, possibly some rectangular raster scans/pointed observations of features of interest). |
The distribution of exposure time over the sky differs substantially and complexly between the two pipelines. Even in areas in which they both have coverage, there are different areas in which each pipeline netted more exposure time. The reasons for these differences are under investigation, and are likely not limited to the Attitude Correction alone. | ||
| Vignetted edges of the bandpass in hyperspectral maps | Trimmed off | Left in for users to trim off themselves |
| Specially-reduced images from pointed observations of the Vela supernova remnant | N/A | See Vela Imaging Reduction |
| Extracted stellar spectra/catalog | See Extracting Stellar Spectra | N/A |
| Averaged intensity maps | Maps averaged over each band provided for all shutter/star-removal/resolution combinations | The SPEAR team does not provide maps averaged or integrated over the whole band. However, if desired, users can easily produce these by integrating the SPEAR hyperspectral maps over wavelength, as demonstrated in Tutorials. |