JCMT Note from the Director

Note to JCMT Users

Status of the JCMT Carousel

The good news is that one half of the JAC 'Tiger Team' managed to get the carousel operating 'normally' on two motors over a week ago. However, they had very grave misgivings about even attempting to get the third motor system repaired and this is now completely isolated. As the web page notes, the carousel motor control current system is well past obsolete and even the manufacturer has no documentation or support. While this repair work was going on, the other half of the team worked on specifying a replacement system that would also incorporate the carousel speed up project that has been on-hold for the past three years.

Following two intensive design review meetings at the JAC, the replacement system has now been ordered. The initial hope was that it would be installed at the end of this month and into early August. This was an extremely tight schedule however and given the news regarding SCUBA (see below) it has now been decided that to minimise the overall telescope downtime for SCUBA the carousel motors will be replace most probably during late September and early October. This is still very tentative as a lot of schedule reshuffling needs to be undertaken and observers consulted. watch the web and schedule for updates.

The new carousel motor drive system is completely modern, has a digital control system, and is fully capable of providing the necessary carousel speed-up in due course. This by itself will bring a notable improvement in observing efficiency.

Users should be extremely grateful to the JAC 'Tiger Team' and their colleagues who put in lengthy hours and lots of innovative thinking to arrive at the current excellent outcome in such a short time. The down-time so far has been notably minimised; in a worst case scenario we could have been off the air for up to six weeks.

Status of RxB3

Again, thanks to excellent and very lengthy work at the summit by Rob Christensen (ably supported by Henry Matthews and many of the ETS and software groups) RxB3 is now back on the air and operating well. The web-page gives more details. The receiver team are confident that this extensive work (RxB3 was off out of service for 2 months) has cured the well known problems afflicting it. Users can now revel in its high sensitivity, ease of use and newfound reliability. The second replacement (tunerless) mixer for RxB3 is expected to be installed at an appropriate time later this year.

Status of RxA3

With RxB3 coming back into service and RxA3 having a hold-time of only three days, we now intend to remove it from the telescope from July 20th and investigate the problem further. Stephan Claude from HIA will be coming out to help with the strip-down. The outcome might be a relatively simple cryogenic fix which could be done in Hilo, or it might entail shipping the dewar back to the UK for specialist repairs. We hope to have RxA3 returned for the 'A3 slot' in something like December. We also hope to install a replacement mixer in A3 while it is out of service, but this is the subject of ongoing discussions with HIA regarding availability of a mixer and associated staff.

Status of SCUBA

SCUBA is now warm and stripped-down. The new ribbon cables are about to be installed along with other improvements. The surface finish of one interior and one external mirror has very kindly been measured by Taylor Hobson in Chicago. Unfortunately, we have just been notified that the main feature of the upgrades, the replacement filter set and new blockers from QMW, will not now be available in time. This is a big disappointment and a notable step-back as this upgrade schedule has been fixed for almost six months and has involved assistance by visiting staff from the UKATC.

Because we wish to minimise the overall loss of SCUBA time for users, we want to match its downtime with the carousel downtime. The original schedule for the carousel repair would have allowed this, but due to the uncertainty of when the new filters might eventually arrive, we intend to get SCUBA back on the air as planned and then warm it up again at about the same time as the revised carousel downtime (see above). Therefore SCUBA should be back in service on August 5th for a period of what is currently anticipated to be around six to seven weeks before the warm-up to install the filters.

Information for the progress on all these projects will be found on the web pages. This has been another very intensive period for the JCMT and a tribute to the staff of the JAC and their colleagues in the supporting instrument labs in the UK and Canada.

Professor Ian Robson