The Outer Solar System Origins Survey (OSSOS) observations are acquired in blocks: contiguous patches of sky formed by a layout of adjoining multiple 0.90deg2 MegaCam fields. The OSSOS discovery and tracking program uses the Canada-France-Hawaii Telescope (CFHT) MegaPrime/MegaCam.
This paper covers OSSOS blocks that had their discovery observations in 2013A (2013 is the year that the discovery observations were successfully made, and A indicates the half-year semester of discovery opposition; A for Northern spring).
The 2013A blocks were 13AE,
centered at R.A. 14h20m, decl. -12°52' at discovery, spanning
ecliptic latitude range b=0°-3°, and 13AO, centered at R.A.
15h57m, decl. -12°30' at discovery, spanning ecliptic latitude
range b=6°-9°. The sky locations of the 13A blocks are at
44° and 30° galactic latitude.
The 13AE discovery triplets were taken under some minor (<0.04mag) extinction and with IQ that ranged from 0.65'' to 0.84''. The 13AO discovery triplets exhibited no extinction and IQ that ranged from 0.49'' to 0.74''. Subsequent imaging to track the discoveries was acquired through 2013 August. Not all discoveries were observed in every lunation due to objects falling in chip gaps or on background sources on some dates, faint magnitudes, or variable seeing in the recovery observations.
For the seven February-August lunations that the blocks were visible in 2014, the 13AE and 13AO discoveries brighter than the characterization limit (Section 5) were observed with pointed recoveries
Data acquisition : from 1 Feb 2013 to 31 Jul 2014
Data provision : 18 Apr 2017
Metadata record :
Creation : 15 Jul 2020
Formats : application/fits, text/csv, text/html, text/plain, text/xml
Data acquisition methods :
- Observational data :
Astrometric observations of TNOs from CFH Telescope.
The OSSOS discovery and tracking program uses the CFHT MegaPrime/MegaCam (Boulade et al. 2003). In 2013 and 2014, the MegaPrime/MegaCam focal plane was populated by
thirty-six 4612×2048 pixel CCDs in a 4 by 9 arrangement,
with a 0° . 96×0° . 94 unvignetted field of view (FOV)
(0.90 deg 2 ) and 0 05 full width at half maximum (FWHM)
image quality (IQ) variation between center and edge. The plate scale is 0 184 per pixel, which is well suited for sampling the 0 7 median seeing at Maunakea.
Our integration length was set at 287s. This exposure length
achieves a target depth of m r =24.5 in a single frame in 0 7 median CFHT seeing.
The OSSOS project has used a dense (for outer solar system
surveys) observing cadence to provide tracking observations
that enable orbital solutions within the discovery year. In the
discovery year we observed in each lunation that a given block is visible. These observations evenly bracket the date of the block’s opposition: precovery in the months before, discovery observations at opposition, recovery in the months after (Figure 2). Precovery and recovery observations on each field of each block were either a single image or a pair of images spaced by at least an hour. Each field of a block was imaged at least 19 times in the discovery opposition.
For the seven February–August lunations that the blocks were visible in 2014, the 13AE and 13AO discoveries brighter than the characterization limit (Section 5) were observed with pointed recoveries; this was possible because the high-
frequency cadence in the discovery year shrank the ephemeris uncertainty to a tiny fraction of the MegaPrime FOV.