# Full-sky 2MASS PSC output

This directory is generated, not versioned.  Create it with:

```sh
python3 scripts/download_2mass_psc_all_sky.py --plan
python3 scripts/download_2mass_psc_all_sky.py --download --workers 2
```

The acquisition uses fixed final integer indices: `ra_index = 0..359` and
`dec_index = 0..179`. Each ownership cell is `[ra_index, ra_index + 1) x
[dec_index - 90, dec_index - 89)` in ICRS degrees, except that `dec_index=179`
also owns Dec `+90`. To avoid polar over-fetch, each latitude band is acquired
through wider integer-RA cover sectors. A cover owns a disjoint run of final
tiles and its one-degree cone contains every point it owns; cone overlap is
therefore discarded by ownership rather than a whole-sky de-duplication table.
Raw responses and cleaning intermediates are in `/tmp/2mass_psc_all_sky/` and
are deleted after each successful cover. `.done/` makes reruns resume after
completed final tiles.

Downloads stay serial to be considerate of IRSA, while `--workers N` cleans up
to `N` already-downloaded covers in parallel. The queue is bounded to `N`, so
temporary raw/intermediate storage cannot grow without bound. Start with
`--workers 2`; increase it only if CPU and `/tmp` headroom remain available.

Each atomic output CSV uses the renderer's four-column CSV format and has a
name such as `tile_ra129_dec109.csv`, which means RA `[129, 130)` and Dec
`[19, 20)` degrees. For any coordinate, use
`ra_index = floor(RA_deg mod 360)` and
`dec_index = min(179, floor(Dec_deg + 90))` to select the filename directly.
It applies the same three-band `rd_flg`/photometry selection and blackbody fit
as the sample processor. The downloader fails if an IRSA response reaches
`--outrows`, so crowded fields cannot be silently truncated. It deletes raw
tile tables after successful cleaning unless `--keep-raw` is passed.

The two existing fields imply roughly 15--17 GiB of cleaned CSV for the full
PSC. Their raw response rows imply 70--75 GiB if every source appeared once.
The cover grid uses substantially fewer cone areas than the old fixed-grid
fetcher, but retaining every overlapping raw response would still need roughly
190--210 GiB. The default bounded pipeline only needs up to `--workers` raw
responses and intermediates in addition to final output.