Wide-field Infrared Survey Explorer

When WILL NEOWISE-R observe a source?

NEOWISE-R is scanning ±92.5o from the Sun in ecliptic longitude. This FORTRAN code will compute the dates that a given position will be on the scan path. Positions are entered in either celestial (RA,Dec) or ecliptic or galactic (lat,long). For celestial type "C" means the input is hh.mmss,dd.mmss while for type "D" the input is RA,Dec in decimal degrees. Types E and G are also decimal degrees. These dates can be off by one or two days depending on the Moon phase.

ned% ./NEOWISER-when
Enter Type(E/C/G),long,lat:C9.5542,+60.4026
(l,b) =  151.851  45.353
 9h55m42  60d40.4
(lambda,beta) =  125.936  44.374

When DID WISE observe a source?

WISE generally observed a semi-circle at an ecliptic longitude 95o larger than the ecliptic longitude of the Sun (blue curve below), and another semi-circle at an ecliptic longitude 90o smaller than the ecliptic longitude of the Sun (red curve below). The asymmetry allows WISE to recover from a brief safing event by decreasing the ecliptic longitude of the scan circles by 1o per day of duration for the safing event. This does not cause WISE to scan any closer to the Sun.

The graph above shows the actual ecliptic longitude of the scan semi-circles as a function of day of 2010, for actually executed survey scans. There were small toggles on every other orbit to smooth out the influence of the South Atlantic Anomaly, and a monthly sawtooth designed to get data before or after the Moon crosses the scan circle. While WISE plans to never look at the Moon, we will collect and throw data with the Moon closer than 15o to the line-of-sight. The monthly sawtooth motion covers these Moon affected regions twice so the WISE catalog will not have holes caused by the Moon. Just as the Moon crosses the scan circle the longitudes are modified to keep 5o away from the Moon. Some test scans were executed trying to exactly match previous or planned scans in order to measure non-linearity in the arrays, leading to the stray dots not on the plan.

It should be possible to find the dates a source was observed by computing its ecliptic longitude, adding a ±0.4o/cos(latitude) range, and then finding the date(s) when the above curves are in the source's ecliptic longitude range.

The map below shows the actual survey plus pretty good IOC coverage in galactic coordinates:

UPDATE: The low coverage that used to be seen along the galactic plane was caused by error returns from the preliminary processing pipeline in this very bright and source rich region. As of 21 June 2010 all these data have been reprocessed so the galactic center hole is filled in.

The actual coverage achieved in WISE band 4 (22 μm) is shown in the map below:

Over 99.99% of the sky is covered 7 or more times, and 99.92% of the sky is covered 8 or more times.

The actual coverage achieved in WISE band 3 (12 μm) before the increased backgrounds from the telescope warming to 45 K required a reduction in exposure time is shown in the map below:

Coverage continued with Band 3 at reduced sensitivity until 29 Sep 2010.

The full coverage for the cryogenic mission is shown in the map below. Data continued to be collected in bands 1 and 2 for the NEOWISE asteroid search program but this map shows the extent of the final data release due in 17 months (01 Mar 2012 [TBD]):

The two band data collected from October 2010 through Jan 2011 will not be included in the final data release but will be available as individual images.

Last modified 24 Jan 2014