Proposal:
2013A-0214
Target of Oportunity:
No
Time Observed:
6.75
Time Engineering:
0.0
Time lost technical:
1.75
Time lost weather:
0.0
Time lost other:
0.0
Description:
Optical transient search
Primary Investigator:
Edo Berger
Email:
Institution:
Harvard
Instrument:
CTIO 4m DECam
Organization:
NOAO
Total Program Time:
8.5
Had the telescope support re-set SISPI this afternoon. During the night, the telescope control system lost communication with the telescope mount three times during the night. We first noticed this when our script directed the telescope to slew to a new position and it did not slew, even though the next exposure in the script would start as normal (just in the wrong, un-slewed position). We paused our script. The TO (Leonardo) reset the TCS. We then slewed the telescope to a field nearby to our desired field coordinates and took a short test exposure, ran "center", and told the TO to re-set the zeropoint based on the "center" output. For the three separate times this happened, the offset output from "center" in arcseconds was (-26,+281), (-62,+290) and (-76,+52). We then slewed to our desired field coordinates with the re-set zeropoint and resumed observing, with everything back to normal and the pointing very good. This cost us ~20-30 minutes each time it happened, resulting in 1 hr 25 min lost. For the past four nights, we have not run into this issue.
There were two times with an OCS error, one of which was at the same time as the mount error described above. The second time, a simple re-set in the System Controls tab set things back to normal.
The pointing model is similar to that described in the 4 previous nights. From running "center" on our images after setting the zeropoint, the RA would generally be at -1-5" offset and then over 45-60 minutes of exposures, would become -10-15" before we would re-set. The Dec "center" offsets were less variable, generally staying <5".
Finally, the disk /home4 became 100% full (2.7 Tb capacity) at ~6:20a local time and we could no longer write any more files. The TO called support who said this problem could not be easily solved and we were not able to immediately change the file-saved path. So we deleted some of our afternoon calibration frames from earlier in the day to make room on the drive and resumed 7 min of standard star fields. Here, we lost ~15 min of observing time trying to figure out this problem.