The VLASS Pilot Survey
The VLASS Pilot Survey
The VLASS pilot survey was carried out during the summer of 2016 to test various aspects of the survey data acquisition and processing. The full requirements and survey definition are given in VLASS Memo #2, the basic survey properties are also listed here.
- Frequency: S-band (2-4GHz), 1024 2MHz channels.
- B-array (2.5" resolution).
- Observing mode: On-the-Fly (OTF) mosaics scanning in RA at constant Dec.
- Mapping speed ~20deg/hr (including overhead).
- 196hr total duration.
The observations were designed to map to key areas that are needed to inform the final survey design and provide observations of well-studied fields that will enable comparison with prior data, both at radio and other wavelengths. The areas we wished to explore were:
- Imaging of time variable sources.
- How the noise reduces with integration time.
- Transient detection algorithms.
- Imaging of compact sources.
- Imaging of extended sources.
- Completeness and reliability for compact sources.
- Completeness and reliability for extended sources.
- Systematics associated with data taking methods.
- Observation failure rate.
- Issues with southern declinations.
- Issues with very bright sources.
- Issues with fields transiting near zenith.
- Operational and post-processing workflow issues.
- Polarimetry.
The pilot survey fields:
| Field | RA (hr) | Dec (deg) | Footprint* | Observation | Area (sq deg) | # hrs |
|---|---|---|---|---|---|---|
| COSMOS | 10 | +2 | 145 0, 145 8, 155 8, 155 0 | 3 epoch OTF | 80 | 12 |
| Cygnus | 20.5 | +40 | 303 37, 303 45, 316 45, 316 37 | 3 epoch OTF | 80 | 12 |
| Cepheus | 23.0 | +62 | 333.5 58, 333.5 66, 354.5 66, 354.5 58 | 3 repeat OTF | 80 | 12 |
| CDFS | 3.5 | -27 | 47.44 -30, 47.44 -22, 58.57 -22, 58.57 -30 | 3 repeat OTF | 80 | 12 |
| Galactic Center | 17.8 | -29 | 260.68 -33, 260.68 -25, 272.12 -25, 272.12 -33 | 3 repeat OTF | 80 | 12 |
| Stripe 82 | 21-03 | 0 | 300 -1.21, 300 1.21, 60 1.21, 60 -1.21 | 3 epoch OTF | 320 | 48 |
| SDSS SGC | 21-03 | 0 | 308 1.21, 308 13.21, 31 13.21, 31 9.21, 48 9.21, 48 1.21 | single OTF | 1360 | 68 |
| Lockman | 11 | +57 | 152.6 54, 152.6 62, 171.4 62, 171.4 54 | single OTF | 80 | 4 |
| ELAIS-N1 | 16 | +54 | 234.3 51, 234.3 59, 251.7 59, 251.7 51 | single OTF | 80 | 4 |
| HATLAS-N/Bootes-1 | 14.5 | +34.3 | 211.4 30.3, 211.4 38.3, 223.6 38.3, 223.6 30.3 | single OTF | 80 | 4 |
| HATLAS-N/Bootes-2 | 13.2 | +28.0 | 192.3 24, 192.3 32, 203.7 32, 203.7 24 | single OTF | 80 | 4 |
| GOODS-N | 12.6 | +62 | 178.3 58.2, 178.3 66.2, 199.7 66.2, 199.7 58.2 | single OTF | 80 |
4 |
*Footprints are the corners of the coverage polygons in the form RA1 Dec1, RA2 Dec2 etc with RA and Dec in degrees.
VLASS Pilot Sky Coverage:
Data Policy
Raw data from the VLASS pilot is available immediately via the NRAO archive, stored under project code TSKY0001. Once data products have been made and passed our quality assessment they will also be available from the archive. In the meantime, interested astronomers are welcome to join a Science Working Group (via the Google Group) to obtain access to the preliminary products while they are being validated.
Please use this public GoogleSheet, NRAO VLASS Pilot, to find the associated file names (FSID) in the archive, the status of basic pipeline processing, any known potential issues (note in particular that the pointing tables in the data should not be used, taken prior to 2016 August 11 have very bad pointing tables, after date that we believe there is still a timing offset).
