SPHEREx Simulated Data for January 2025 AAS
The SPHEREx project is providing example data files to help the community understand the SPHEREx data. For more information about SPHEREx, see spherex.caltech.edu. Every 6 months, SPHEREx will conduct an all-sky survey from 0.75 to 5 microns. The sky is surveyed by taking a series of wide-field exposures, at an average rate of approx 500 per day during the 2-year prime mission. The key instrument feature enabling the science is the use of linear variable filters (LVFs) in front of the detectors. These enable spectroscopic measurements to be made very efficiently over wide fields and results in every detector pixel being a spectral-spatial element. The instrument takes an exposure with six detectors, each 2k x 2k pixels, every 120s during mission operations.

Science Level 1 to Level 3 data processing will be carried out by the SPHEREx Science Data Center (SSDC) at IPAC. Level 2 files are photometrically and astrometrically calibrated images with the wavelength profile of the linear variable filter (LVF). These example files were produced by generating instrument-sampled sky scenes with the SPHEREx Sky Simulator and processing those images in the SPHEREx data pipeline to Level 2 and generating example photometric measurements from one of these files.

IRSA will provide a dedicated interface for the SPHEREx public data, which will include standard search, retrieval, and visualization capabilities, including the use of IVOA-standard interfaces. In addition, IRSA will host SPHEREx specific search, retrieval and analysis tools, including user-driven photometric measurements.

Example Images: Two fields were selected to show examples scenes both within the Galactic plane and at higher latitude. All detectors are provided for each position. These files with simulated data are provided for the community to see the SPHEREx data format, in particular how the wavelength changes across the detector. Note that small changes to the headers may be made when on-sky data are released. The python notebook linked below includes a description of the data layers and a demonstration of how to access them.

Example Photometry: An example photometry file is given for a generic field, detector 4, which contains wavelengths from 2.3 to 3.9 microns. Note that this is the single integration photometry for all sources in the field. Once the data are available in IRSA, users will be able to request photometry per source, which will be aggregated into a spectrum by combining measurements from many observations of the source at different locations on the LVFs.

Viewing the images: IRSA Viewer, based on IPAC Firefly can be used to visualize these calibrated images, including the per-pixel wavelength. IPAC Firefly can also be used locally, most conveniently by downloading a Docker image. If you use other tools, the per-pixel wavelength WCS layer may not display. Note that for DS9, you need to use a version later than commit 3d5bda9.

Data Set Characteristics

Data ProductDescriptionData Access
Images Simulated data for January 2025 AAS
Spectroscopy Photometry Parquet file
Software Python notebook