Second Quarter 1999

Most of the mechanical work this quarter focused on assembly and integration of the cryostat mechanisms into the cold structure. All the parts remaining from outside vendors were finally delivered by May. Fabrication of the slit-viewer optical mounts, dichroic turret and detector assembly cold straps in the IfA machine shop was stopped for two months while priority was given to the Near-infrared Imager (NIRI) being built for Gemini North. However, by the end of June, 95 percent of the cold structure and all the mechanisms had been integrated into the cryostat in preparation for the first cold test of all the mechanisms and the detector assembly cold straps. In readiness for this test, assembly of the instrument control computer (Little Dog) was completed in May together with some of the software required for mechanism control.

A goal of the cryo-mechanical design was to provide for servicing and removal of individual mechanisms, optics, filters, detectors and closed-cycle cooler, without the need to remove the cold structure from the cryostat and with minimal disassembly, while guaranteeing light-tightness of the optical path. The all-up assembly test in June identified the grating turret as the only significant access problem. This will require modification to the grating turret access covers.

Final design of the grating turret prism and grating mounts, and final design of the cryostat telescope mount and calibration box, were started this quarter and will be completed next quarter. The calibration box optics (lenses, mirrors and integrating sphere) have all been delivered, and the QTH lamp, IR source, argon lamp, and associated power supplies, are on order.

In April IRTF joined a consortium buying broad- and narrow-band infrared filters from NDC Infrared Engineering, UK. The filters will be used in both SpeX and NSFCAM.

In May we took delivery of four 512x512 InSb arrays made by Raytheon (formerly Hughes SBRC) as part of the PAIDAI project. The arrays are being tested and evaluated for NASA and the PAIDAI partners. SpeX will use the best device in its slit-viewer. Testing is being done in the lab test dewar using the Guide Dog (slit-viewer) array controller.

In software developments, work continued on refining array control and increasing speed. A first attempt at a movie mode for Guide Dog was implemented and the disk size increased to 9GB to store movie/occultation mode data. For the SpeX GUI interface it was decided to replace Motif with the more flexible GTK+ toolkit. The GUI applications are being rewritten. To meet the speed specification to support high speed spectroscopy for occultations, Bigdog's Sparc5/64 was replaced with an UltraSparc IIi, and all the Unix software upgraded to work under Solaris 2.6.

Photos from this quarter:
Cold structure mounted inside cryostat vacuum jacket. The spectrograph box is on the left, the slit-viewer is in the centre, and the fore-optics is on the right, all surrounded by the cold shield, and shown with the front and back covers of the cold shield and vacuum jacket removed.
Cold structure viewed from the back (motor feed-through) side.