Second Quarter 2000

SpeX was shipped from Manoa to Mauna Kea on Friday April 28 and arrived safely at IRTF on Wednesday May 3. The cryostat, electronics, computers and ancillary equipment were packed into a freight container which was driven to Honolulu docks, transported by barge to Hilo, and then driven directly to the summit. Shock sensors mounted to the cryostat indicated that the largest shock sustained during shipping was 5G, well within safe limits. Following unpacking and evacuation, and with SpeX fully cabled-up in the Visitors Prep. Room, cooling was started on Saturday May 6. Cold tests on Sunday and Monday indicated that everthing was working well and on Tuesday May 9 at 12.45am SpeX was bolted to the telescope. At 12.50am it still hadn't fallen off. With SpeX in its stow position on MIM the telescope was successfully balanced and slewed around the sky to check clearances with the telescope mount. With the instrument fully cabled-up later that day, array noise tests reproduced the low noise measured in the lab. The following day SpeX was moved into the on-axis position and the telescope rebalanced using the new moveable counterweights. During rebalancing the telescope instrument rotator slipped causing the cryostat to rotate about 30 degrees. Fortunately no cabling was strained but the rotator had to be immobilized. Better brakes are being designed.

First light with SpeX was successfully accomplished on the first night of the May 16-18 engineering run. During this and the May 24-26 engineering SpeX was tested in most of its observing modes and performed extremely well. The average throughput (removing slit losses) of the spectrograph in cross-dispersed mode was about 15%, with a peak throughput at the grating blaze angle of about 25%. Throughput was even higher in the prism and single order modes. The throughput of the infrared guider/imager was about 25%. With multiple reads the spectrograph array readnoise was 15 electrons RMS and the dark current less than 0.3 electrons per sec. The only significant performance issue was a significant fall in throughput below 0.9 microns. This was traced to a problem with the anti-reflection coatings on the ZnS lenses and ZnSe prism. (These components were repolished and recoated during scheduled downtime in August.) Following the two engineering runs, SpeX was used for shared-risk science runs by Hammel, Bendo, Rayner, Gaffey, Vacca, Spencer and Brooke during June and July. The functional performace was virtually flawless during these runs (mechanisms, electronics etc.), with only four hours lost to a disk crash in the motor-controller pc. The Graphical User Interface worked well from the start.

The only software which required sinificant development during commissioning was control for the infrared guider. This was to be expected since IR guiding is new to IRTF. The basic guider algorithm worked well but the user control of the guider was updated as we learnt how best to use it. By the end of July the guider was working well in all its modes. The magnitude limit for guiding on spill-over from the slit is about J=15 for auto-guiding and about J=18 for manual guiding.

This quarter's photo directories:

    2000-04-25-preshippment - Spex in irlab before shipping to the summit.

    2000-05-09-preprm-to-cass - Spex in the summit prep room and being mounted on the telescope.

    2000-05-16.1st-engineering - Spex 1st Light on the IRTF.