A1956 alfa precursor proposal: extra galactic ultra deep survey


28sep04:  A1956 first use of driftchase pattern. pixel positions off at the start.
21oct05: A1956 drift chase pattern. updated position errors.


    Project a1956 is one of the alfa precursor proposals. It will do multiple drift scans (78 seconds drift, then reacquire the start of the strip) to increase the integration time of the map.

28sep04:  A1956 first use of driftchase pattern. pixel positions off at the start.  (top)

    Project a1956 took some data on 28sep04 to test things out. It used the driftchase pattern. The drift scan lasted for 78 seconds. For one of the scans the ra/dec positions for the pixels were off at the begining of the scan (all scans were not checked). These are the values stored in crval2a,crval3a of the fits header. The plot shows the ra,dec positions (.ps)  (.pdf) . These are for pixel 0 (the central beam).

21oct04:  A1956 drift chase positions after working on pattern.   (top)

    Project a1956 started their observing run on 21oct04. The drift chase procedure had been worked on to correct the positioning errors seen on 28sep04.  On 21oct04 5 driftchase scans were done each lasting 80 seconds. I took the ra/dec positions from the header (crval2a,crval3a) for beam 0 and  compared them with ra/dec positions computed using the encoder az, za, and encoder time (interpolated to the data times in the header). The plots show the ra,dec positions (.ps)  (.pdf) . The ra,dec positions from the header values crval2a,crval3a has improved. It  jumps around by about +/- 7 asecs max for this data set. The az,za encoder values changed by at most  1 arcsecond, so the jumping around is a computational problem and not the telescope moving.