astro-legacy-archive/galex-gphoton

GALEX gPhoton raw6 eclipse 10830

This dataset contains the source FUV and NUV GALEX RAW 6 tables for eclipse 10830: 81,933 and 20,426,980 rows respectively, in source row order. Both artifacts retain the shared 1,904-row S/C State Data table in their event-list self-description. These files are raw time-tagged photon telemetry used by the gPhoton calibration pipeline, not gPhoton's calibrated, sky-projected database product. The packed photon bytes are not decoded.

How to use

from datasets import load_dataset
dataset = load_dataset("astro-legacy-archive/galex-gphoton", "e10830-fd-raw6", split="train[:1]")
print(dataset[0]["t"], dataset[0]["flags"])

799657803.00452 0

import json
from huggingface_hub import hf_hub_download
import pyarrow.parquet as pq
path = hf_hub_download("astro-legacy-archive/galex-gphoton", "e10830-fd-raw6.parquet", repo_type="dataset")
print(json.loads(pq.read_metadata(path).metadata[b"event_list"])["event_extname"])

GALEX RAW 6

Source unit and integrity

The raw-file resolver returns exactly three files for eclipse 10830, in this order: the shared spacecraft-state file with band BOTH, the FUV raw6 file, and the NUV raw6 file. The resolver response uses HTTP; the pinned files use the same paths over HTTPS.

• e10830-scst.fits.gz: source, SHA-256 27ad66d4f4d331ec89bd50946fb17259fee868c7bb29c396a533fe3f27b7e9f0 (400659 compressed bytes).
• e10830-fd-raw6.fits.gz: source, SHA-256 328ae734ee2a9966c5efd522d3e98101a074bd85ba666c8015ab729b26ccc0b5 (752317 compressed bytes).
• e10830-nd-raw6.fits.gz: source, SHA-256 7667e03f967ba2b8c1e4bc611f02642d6f42e477c20869b102b2ad533e2effc5 (187685553 compressed bytes).

Resolver endpoint: eclipse 10830 raw-file response. The three-file unit is 188838529 compressed bytes. All three gzip streams pass gzip -t.

Photon-table structure

Each raw6 file has a zero-length primary image followed by a FITS binary table with EXTNAME='GALEX RAW 6', row width 16 bytes, and eight columns in this exact source order:

• t: TFORM=1D, TUNIT=seconds, source photon timestamp.
• phb1: TFORM=1B, TUNIT=n/a, packed photon data byte.
• phb2: TFORM=1B, TUNIT=n/a, packed photon data byte.
• phb3: TFORM=1B, TUNIT=n/a, packed photon data byte.
• phb4: TFORM=1B, TUNIT=n/a, packed photon data byte.
• phb5: TFORM=1B, TUNIT=n/a, packed photon data byte.
• phb6: TFORM=1B, TUNIT=n/a, 8-bit time offset from the photon header time.
• flags: TFORM=1I, TUNIT=bits, source flags field.

The raw GALEX documentation describes phb1 through phb6 as packed photon X, Y, Q, XA data. PhotonPipe consumes t directly, bitwise-decodes phb1 through phb5, and does not read phb6; it then applies detector, distortion, separately obtained aspect, and sky-projection calibrations. The decoded or calibrated x, y, xi, eta, ra, dec, and q values are therefore not columns in this mirror.

The gPhoton code converts a source timestamp to Unix time by adding 315964800 seconds, identifying the source epoch as 1980-01-06T00:00:00. Raw photon times retain the source clock and must not be treated as calibrated UTC without the documented clock conversion and calibration caveats. GALEX absolute timing is accurate only to about 1--10 seconds because of spacecraft-clock uncertainty; relative timing within an observation is better than roughly 0.005 seconds. On leap-second days relative times can be wrong by as much as one second.

FUV timestamps are source-row monotonic and distinct. NUV retains 40,737 descending adjacent steps and 2,831,399 equal adjacent steps. The source flags field is exactly zero throughout both tables; it is not a validity mask or GTI.

Spacecraft-state companion

There is no FITS GTI extension. Valid exposure depends on time-resolved spacecraft state/aspect flags and detector high-voltage state in the shared S/C State Data companion. It has 1,904 rows, row width 560 bytes, and 105 columns in source order. No TUNIT cards are present for those fields.

The metadata snippet above gives the precise route to this embedded table: event_list -> auxiliary_tables[0]. Its columns array preserves every source field's name, tform, source dtype, and values; names and values are not normalised. The fields cover pktime, spacecraft flags and pointing, detector high-voltage and dead-time state, quaternions/aspect data, and comment. Use this self-description for state and validity interpretation rather than treating raw6 flags=0 as sufficient.

The raw-file-resolver unit is not the complete calibration input set. PhotonPipe documents generation from mission raw6, scst, and asprta data; its separate aspfile input is obtained with web_query_aspect(eclipse) when none is supplied.

Rights, credit, and citations

MAST states:

Most data hosted at MAST are in the public domain (see: open data), and therefore do not have restrictions on use. There are, however, expectations (or in some cases, requirements) that researchers acknowledge the originating mission and (usually) STScI in all scholarly publications.

It also states:

Following the expiration of the applicable exclusive access period, science data become available for public use without restriction.

Source: MAST data use. This public-domain statement is represented as other.

Requested acknowledgement:

If you use gPhoton for your research, please cite: Million et al. 2016, ApJ, 833, 292.

Cite Million, C. et al. (2016), “gPhoton: The GALEX Photon Data Archive,” The Astrophysical Journal 833, 292, DOI 10.3847/1538-4357/833/2/292, arXiv:1609.09492, bibcode 2016ApJ...833..292M. The associated archive product is DOI 10.17909/T9CC7G and the software record is ASCL 1603.004.

For GALEX calibration and mission data products, cite Morrissey, P. et al. (2007), “The Calibration and Data Products of GALEX,” The Astrophysical Journal Supplement Series 173, 682--697, DOI 10.1086/520512, arXiv:0706.0755, bibcode 2007ApJS..173..682M.

MAST announced that it will discontinue the separate precomputed calibrated gPhoton service on 2026-12-07 because gPhoton2 supersedes it. The announcement does not say that these pinned raw6 archive inputs will be removed.

Errata and requests

Report corrections or dataset requests in the dataset's Community tab.