3.7 Hubble Advanced Spectral Products (HASP)
The Hubble Advanced Spectral Products (HASP) program provides one-dimensional spectra for HST spectroscopic data through the use of the Mikulski Archive for Space Telescopes (MAST). HASP provides coadded and combined products for STIS and COS spectra. By default, combinations of different gratings, central wavelengths (CENWAVEs), or apertures for individual programs are not provided, necessitating users to manually coadd spectra for scientific analysis. HASP automatically coadds most datasets and provides tools for users to create custom coadds. Custom coadd options are provided in Jupyter Notebooks. Please note that HASP products created for extended and variable objects may not be accurate. In those cases, it is recommended to use custom coaddition.
3.7.1 Data Products
The coadd code implemented in the HASP project generates two distinct data products: coadds and abutments, created at both the visit and program levels. Co-added spectra are the result of combining spectra from a common grating, while abutments involve the combination of spectra from different gratings and/or instruments.
Naming Convention
Program-level co-add files follow the format:
hst_<PID><instrument><target><opt_elem><ippp>_cspec.fits
Visit-level co-add files follow a similar, if slightly different format:
hst_<PID>_<instrument>_<target>_<opt_elem>_<ipppss>_cspec.fits
where:
- <PID> is the program ID, e.g. 11068
- <instrument> is the instrument used (one of COS, STIS, OR COS-STIS)
- <target> is the target of the observation, e.g. "NGC5457"
- <opt_elem> is the optical element (i.e. filter or grating), e.g. "G140L"
- <ippp> is the instrument and program ID of the program level coadd, e.g. ld5z (where l = COS and d5z = Proposal ID 14772)
- <ipppss> is the instrument, program ID, and observation ID of the visit-level coadd, e.g. Id5z20 (visit 20 of the above example)
FITS Structure
The FITS file structure for these co-added products consists of two BINTABLE extensions: a Science extension containing specific information about the combined product and a metadata extension recording attributes of each spectrum contributing to the combination.
Table 3.6: The science extension table stores data elements of a single spectrum.
| Keyword | Units | Type |
|---|---|---|
| WAVELENGTH | Angstrom | single-precision float |
| FLUX | erg/cm2/s/Angstrom | single-precision float |
| ERROR | erg/cm2/s/Angstrom | single-precision float |
| SNR | --- | single-precision float |
| EFF_EXPTIME | s | single-precision float |
Table 3.7: The provenance table contains metadata from the headers of contributing spectra.
| Keyword | Units | Type | Description |
|---|---|---|---|
| FILENAME | -- | string | Input spectrum filename |
| EXPNAME | -- | string | Exposure name, if multiple spectra per file |
| PROPOSID | -- | string | Proposal ID |
| TELESCOPE | -- | string | Observatory |
| INSTRUMENT | -- | string | Instrument |
| DETECTOR | -- | string | Instrument detector |
| DISPERSER | -- | string | Grating |
| CENWAVE | -- | string | Central wavelength of grating |
| APERTURE | -- | string | Aperture selected |
| SPECRES | -- | double-precision float | Estimated spectral resolution |
| CAL_VER | -- | string | Calibration version |
| MJD_BEG | d | double-precision float | Exposure start time (MJD) |
| MJD_MID | d | double-precision float | Exposure mid-point (MJD) |
| MJD_END | d | double-precision float | Exposure end time (MJD) |
| XPOSURE | s | double-precision float | Exposure time |
| MINWAVE | Angstrom | double-precision float | Minimum wavelength |
| MAXWAVE | Angstrom | double-precision float | Maximum wavelength |
Data Access
HASP products are available in the HST search form on MAST or through the MAST portal. The data are also available through the astroquery API. This notebook tutorial provides a walkthrough of how to download and use the HASP co-add script.
Further information regarding HASP, including performance evaluation and caveats is covered in detail in COS ISR 2024-01.