This is the public version of the SAC report for its 50th meeting. Note that some sections dealing with internal issues, and of no interest to the community, have been removed for this version. Members of the SAC present at this meeting were: Claude Catala (chair), Jean-Gabriel Cuby, David Hanes (vice-chair), Paul Hickson, John Hutchings, Gilles Joncas, Pierre-Olivier Lagage, Alain Mazure, Richard Wainscoat. Esther Hu had sent apologies. The open sessions of the SAC meeting were also attended by Pierre Couturier, Director of CFHT, Derrick Salmon, Director of Engineering, Dennis Crabtree, Senior Resident Astronomer, and other CFHT staff. The agenda for the 50th SAC meeting was as follows:
The upgrade of the 9 ton crane's load capacity to 12 tons took place at the end of May. The upgrades required installation of new cable drums, reinforcements of critical components, the addition of travel limit bumpers, and load testing. The crane is now officially rated by Transcrane at 12 tons in accordance with loads associated with the upper ends. An attempt to add load metering using equipment developed by Transcrane was not as successful. This unit and its strain-gauge readout system has been returned to Transcrane for further development. We currently have no load metering capability while handling upper ends. At the same time we took the opportunity to replace electrical cabling between the crane and crane cab due to age-related deterioration.
Office space on the 4th floor has been re-organized to include work space for T.O.s and to add a small document/library facility.
A dome drive friction wheel disintegrated in mid semester and was replaced with spare.
As our contribution to coordinated summit clean up operations organized by MKSS, 6 CFHT staff volunteers spent a day cleaning the mountain slopes and plateau directly to the East of the CFHT building down to about the 11,000 ft level. The team gathered and consolidated trash (new and previously collected) for future removal by helicopter. We also took this opportunity to clean outside our dome building by removing old crates and oil drums.
The f/35 secondary chopper electronics were largely rebuilt after the accident at the start of the year.Much of the cabling was replaced due to damage and reconfigured to significantly reduce system noise and susceptibility to EMI and to make troubleshooting easier. New LVDT's for mirror position sensing were added.The voice coil drivers were replaced with spares, and the damaged units were rebuilt to serve as backups. System mechanics were cleaned, maintained and secured in the Waimea shops before final assembly. The chopping system was thoroughly tuned and tested using a dummy mirror.
The repaired and re-coated secondary mirror was returned from Contraves with essentially the same optical figure as when initially procured according to interferograms provided by Contraves. Intense effort by the electronics and mechanics groups had the system ready at the summit about 1 week before the scheduled July IR observing runs. The system has worked essentially without problem since installation.
The F/8 secondary mirror was successfully re-aluminized and put back into service in August. The aluminizing chamber was prepared for the next coating and large O ring seal on the chamber mating faces were replaced.
Problems continue with the seating of upper ends on the telescope structure during upper end changes. Clearances between the upper end and the telescope's 'bird's head' locks which are designed to be roughly 13 mm are really on the order of 1-2 mm and can occasionally be zero or less.The result is an upper end 'hang ups' while handling - a very serious condition which if allowed to free itself can result in a violent seating of the upper end. The problem is exacerbated by difficulties in accessing the top of the telescope and by the fact that the upper end handling ring completely envelopes the locking system when in the unlocked (problematic) condition.
Inspection of locking segments on upper end handler revealed several and incorrectly sized bolts which resulted in erratic handling ring operation. These where replaces and re-torqued.
Bird's head clearances were investigated with all three top ends on June 5 and 6. Binding in the locking system at this time precluded provision of adequate clearances in the unlocked position. We currently ensure adequate mounting clearances by detailed visual inspection as the top end is put in place. However this lengthy process is not appropriate for the long term.
A short scheduled 3 day shutdown in early September was used for 'bird's head' lock maintenance and investigation. This is the first time since the telescope was assembled that the locks have been disassembled. Custom handling equipment was designed and fabricated to permit removal of the 400 kg locking segments. This equipment worked extremely well. We also purchased a special 3-man 'basket' with dedicated safety harnesses for work around the top of the telescope. Maintenance however is still very crane- intensive.
During this shutdown we were able to service only one of 4 segments in 3 days. Several of 14 wear plates associated with the SE segment showed signs of heavy wear and cracking. Guide bolts were of non-uniform size. Damaged wear plate were replaced. Guide bolts on all 4 segments were inspected and undersized bolts were fitted with precision sleeves. Although this maintenance was clearly overdue, locking systems clearance problems were not much improved. Clearance problems are accentuated by the design of the handling ring's segments which allows the ends of each segment to swing. The swing result in interference as upper ends are seated.
Clearly these systems require a lot more work. We are planning major upgrade/ repair efforts for next summer. In the mean time detailed documentation of as- built dimensions appears to be the only means for resolving inconsistencies between design and operational clearances.
The sources of ongoing intermittent control problem with Z' focus control was identified and solved in June. Old wiring and poor design of its control system continue to make the prime focus bonnette rather unreliable. We are currently pursuing plans to rebuild the bonnette control system in 1997.
Instabilities in the Primary Mirror axial support which have limited use of the telescope to relatively low air-masses has been a severe limitation for IR observers. A detailed review and adjustment of the support systems pneumatic regulators in July largely solved this problem. The piston of one regulator was found to drag slightly. Regulator inlet air pressures were adjusted to establish regulator piston heights according to manufacturer specifications. The telescope can now be used to z = 77 without the primary mirror support system oscillating.
The primary mirror was liquid washed in mid June resulting in a 4.3 % increase of reflectiviity and significant reduction in scattered light.
Dedicated dry air lines and CCD fiber optics cables were run through the cable wraps. We no longer have these systems taped to the outside of the outside cage.
The tacho on an hour angle drive motor failure in mid-semester. Although no significant telescope time was lost, high-current oscillation during telescope slews caused concern until the source of the problem was identified. The faulty motor (tachos are integral to the motor) have been returned to Inland Motors for repair. Several motors - both active and spares - have tacho problems and will be maintained in the coming year. Turn around time is on the order of 4 to 6 months.
An initial thought on the cause of the oscillations was that they might originate with contamination in oil-pad bearing clearances. Accordingly all bearing gaps were thoroughly inspected and found to be well within expected limits.
The spare video image integrator unit (known as Leaky2) that was procured many years ago, was tested, documented and installed at the summit as a "hot spare" to the main video integrator used by the TCS autoguider system. Now if the main video integrator (known as Leaky1) fails (for which there have been several scares), the telescope operator can bring Leaky2 on-line with only a few minutes of down time before autoguiding is restored. The TCS4 project will replace these custom video integrators with a commercial image processing module.
TCS autoguider cabling: connections between the video integrator unit (Leaky1) and the data acquisition system (CAMAC) required cleaning and rebuilding of cable connectors.
Operation of the AOB continues to be straightforward and trouble free. As with other complicated systems, much of the ease of operation on the sky can be attributed to intense run preparation by the technical staff.
The planned purchase of upgraded APD's has been put on hold pending comparative tests between old and new technology APD's (a sample new APD is on loan from the JNLT). Initial estimates of potential gains in sensitivity appear to be overly optimistic. A single APD in the Wavefront Sensor failed and was replaced by a spare.
Optical throughput efficiency calculations of the wavefront sensor subsystem predict a factor of 2.6 higher sensitivity than is measured on the sky, and in the laboratory. Attempts to locate the source of this loss have been unsuccessful to date.
Tests of the 2x focal enlarger for the AOB using FOCAM and STIS were very successful. The system provides critical sampling of the psf below 1.0 um. This system is now an available option for observers.
The focal enlarger was also modified slightly to accommodate our Fabry Perot etalons. The system was successfully tested on the AOB with a comparison spectral source earlier in the semester. We hope to test the combination on the sky in January.
Three new beamsplitters have been ordered for use in the visible with OASIS. The beamsplitters will have bandpasses for the V, R, and I bands These should improve throughput to the WFS by about 50% over the current '50/50' beamsplitter and will increase throughput in the science path to about 90% in the bandpass.
The diameter of the AOB's small artificial star was reduced from 8 microns to 3.0 microns for work at wavelengths in the 0.5 to 1.0 um range. The user interface is now working quite well; the number of system glitches has been reduced to at most one or two a night. Still, substantial improvements to the software are underway to improve overall reliability. The MOSAIC tool used in combination with MONICA has been particularly successful.
Overall ease of use for visiting scientist - one of the initial design goals - has been validated by two observing runs by non-specialist observers. Guide star acquisition and loop closure have proven to be trouble free and straightforward. AOB specialists are no longer required on site once initial observer familiarization has taken place.
A large amount of background work by the technical staff has been aimed at making setup operationally "friendly" through hands-on training and updating of documentation.
Much time was spent preparing and supporting the 27 night run of FTS. The system was operated in several different modes (InSb, InGaAs, BEAR-imaging, and seismology-mode). Time spent earlier in the year to eliminate 60 Hz interference with the InGaAs diodes clearly paid off. These InGaAs diodes provide a 4x to 6x signal gain over the inSb detectors at 1.2 um and are operationally quite easy to use since they require neither a dewar nor cryogenics.
Flexure measurements of the FTS in the BEAR configuration were made to determine if the modifications made to the mounting mechanics of the REDEYE camera had reduced image motion.Unfortunately the stiffer camera mount did not reduce motion in the image plane. The flexure data suggests that the major source of image motion, which reduces BEARs effective FOV by about 10% for long scans, is probably in the optics between the output of the FTS and the REDEYE camera. The upgraded mechanics does however greatly ease the mounting and alignment of Redeye.
The newly re-coated IR1 beamsplitters were installed and worked well. Increasing problems with reference laser throughput for the IR2 beamsplitters causing several servo unlocks during the July / August observing run. Replacement beamsplitters are currently being fabricated (re-coating was not an option). The new beamsplitters should be ready in time for the next FTS runs. The reduced reference laser signal with the IR2 beamsplitters made switching between the beamsplitters difficult and required modifications to the reference signal circuitry.
A new "seismology mode", consisting of small scans (typically 16 steps) around a selected carriage position has been added.
Development of OASIS continues in Lyon. The CFHT Electronics and Optics Group will be heavily involved over the next 8 months to one year with the acceptance and delivery of OASIS instrument. Recently, scheduling issues, as they impact the CFHT staff and requests for observing time at the CFH telescope have been discussed and agreed to by the development team from Observatoire de Lyon in France. Review of the final mechanical, optical and electronics design drawings has just started at CFHT. Over the next three months, members of the CFHT technical and scientific staff will generate an acceptance test plan, which will be used to accept OASIS as a "Guest Instrument".
The cabling and connectors between the octagon and the control electronics rack were completely rebuilt to help with overall system reliability. As a means of reducing power consumption at the cassegrain environment controls for both the Fabry-Perot etalon and the cassegrain spectral lamps have been moved from CAMAC to the MOS / OSIS controller.
MOS / OSIS controller software has been upgraded to eliminate several problems and to provide better test capabilities. In particular, problems with system hangups during OSIS fast guiding should now be solved.
A pair of high resolution IR grisms for OSIS have been received and are undergoing tests. We have also received a replacement for the low resolution H grism which was originally made out of specification.
New light baffles have been fabricated for MOS and OSIS. These should be installed by the end of October. These baffles will hopefully solve light leak problems at the edges of the Prontor shutters.
The inside of the OSIS camera barrel has been painted a flat black in an attempt to reduce the amount of scattered light seen in OSIS. During tests on the mezzanine, a major source of scattered light was identified.
MOS / OSIS setup has represented a heavy load to the technical staff. A great deal of this load is associated with interchanges of grisms between cassettes. A first step in freezing each of the grisms to a specific cassette was started this semester with a contract to DAO for the manufacture of 11 grism cells.
Finally, bi-prism focus capabilities for OSIS and the MOS ARGUS mode has been provided by a pair of new bi-prisms.
A larger 100 mm diameter iris shutter is being added at the detector environment to eliminate vignetting of the 4096 x 200 thinned UBC ccd. A custom driver mechanism for this shutter is being designed to keep power dissipation at the shutter low.
As with MOS / OSIS, the spectrograph's DUCK control software has been updated to improve system reliability.
Work on the fiber feed system is still on hold.
The mask stage motor controls have been significantly updated with a controller which permits rapid mask motion between slits and simultaneous motion of both axes. The new controller also supports cut-file generation straight from AutoCad files.
System safety has been significantly enhanced with the completion of a wrap- around laser shield.
Finally, work has started on a laser auto-focus mechanism to help improve cut precision and speeds.
The existing spectral calibration system available at cassegrain (gumball), will not meet the needs of OASIS when it arrives in 1997, and the existing control system is quite difficult to maintain. A project to "upgrade" the existing gumball to meet the needs of OASIS and be more maintainable is slowly getting started. A rough conceptual optical design to modify the existing lamp holder, and a rough design of the control system have been generated. The detailed design phase for both the optics and control system are expected to occur in the last quarter of 1996 (time allowing). The time line for this project is being driven by the arrival date of OASIS.
The current fleet of CFHT science detectors consists of Loral 3, Stis 2, Redeye Wide, and the Reticon diode array. We currently have 2 2k x 2k thinned ccd's and an engineering grade Hawaii IR array in dewars awaiting tests.
A Residual Gas Analyzer has been added to the Waimea dewar vacuum system. The RGA is proving to be an extremely valuable tool for distinguishing between leaks and outgassing and for measuring their relative contributions to dewar vacuum loss.
This 21 um, thinned, 2k x 2k detector has quickly become the work-horse device. Some initial noise problems during the first run were promptly repaired. A 7 minute readout time was an unpopular feature when this detector was offered initially. Readout has since been upgraded to 2 minutes without significant performance degradation. We are looking into implementing an even faster mode for non-science applications. STIS2 is now offered for use on all CFHT instruments.
The UH 8k detector continues to be used productively at the Prime Focus. There have been a significant number of problems with shutter reliability. During the September run the shutter motor drive shaft had to be replaced - an operation which required the removal of the camera from telescope.Shutter double firing with both shutter leaves actuating at once or in rapid succession resulted in several lost exposures.
Delivery of the camera at the last minute before the observing run has made software integration into the CFHT system more problematic than anticipated. CFHT staff have travelled to IfA with CFHT a computer in order to support the UH software using CFHT facilities. The initial agreement to use the camera software running under Solaris has not panned out so far, although we are still aiming at this target since operation under Solaris will be needed in the longer term.
CFHT received and installed the S-Bus interfaces for the 8k x 12k camera which are currently being used to support runs using the 8k camera. The interfaces are working well.
CFHT has ordered a B filter for use with the 8k camera. Delivery is expected by early November.
Occasional problems with scattered light appears to be due to bright stars catching the edge of the last lens cell in the WFC. We are currently waiting for data from observers so that we can evaluate the effect. Vignetting by the guide probe has been a problem. At the moment we have not been able to provide the observer with an unambiguous range of vignetting- free guide probe positions.. We are working on generating these numbers now.
All scientific data from UH8k runs are saved on exabyte. True archiving will take place later.
The KIR contract with signed University of Montreal was signed in mid July. We are currently expecting delivery to CFHT in March, 1997. The SDSU 4- channel controller was ordered at the end of May and delivered to Toulouse in August. The array controller (SDSU), host computer (Cassini), HP workstation, and preliminary software have been shipped to Observatoire Midi Pyrenees (OMP) where modifications will be made to run the KIR camera system.
A preliminary design review of the dewar has been held, and work has commenced on the optics and software for the system. A final design review is expected in November. We have received the 1K x 1K HgCdTe engineering array from Rockwell and are expecting the science array before the end of the year.
Redesign and reimplementation of the CCD gen III server to allow for support of VME memory access control, data descrambling and raw and reference image data substraction has largely been completed.
This chip, with an engineering grade devices as backup, was to be loaned to CFHT by ESO on a long-term basis. Since the chip was one of a family of ESO chips with a reportedly excellent history, this device was given priority in the CFHT development queue. Unfortunately, after failures of several devices at ESO, their offer was retracted and we are continuing development with a (very good) engineering device. It is worth noting that although the science device had a platinum flash-gate, the engineering device will need to be UV flooded and O2 soaked to obtain the high QE expected of these devices. This project has the second highest priority in the detectors group after KIR.
Dewar preparation at CFHT started in July. Unfortunately the dewar was received with a large number of leaks. Extensive rework of seal surfaces ulimately enabled us to obtain a good vacuum.The detector mounting hardware too placed the ccd significantly off center and off the reference focal surface. These problems have been reworked.
To date a dedicated controller and DSP code updates are complete. The engineering chip is mounted in the dewar. We are awaiting delivery of a final cable this week before tests start.
Problem with a noisy quadrant early in the year were fixed with the fabrication and installation of a new CFHT preamp. Gain with new preamp is 15 e-/ ADCU and noise is 40 e- now set by detector noise limit. Use of the camera with a new controller and Gen III v 4 software needs to be completed. An initial problem with an occasional extra zero pixel prevented the system being used for the FTS Bear run in July. In the mean Redeye use continues with the old controller/preamp system.
The detector MUX was received in mid-May - the engineering device grade in mid- July. A preamp for this camera has been fabricated as a prototype for KIR. The upgraded dewar assembly which permits use of any detector quadrant was received in early June. A few small vacuum leaks were solved in June as was wiring of the bias board. Remaining work includes installation of the new preamp and mount the fanout board and array into the dewar. Testing and optimization will follow.
This detector was intended as an interim AOB detector until KIR could be delivered. In a recent review of project time lines, given the past and expected continued success of MONICA-based AOB runs.and the likely life time for use of Redeye Narrow, we have migrated the project into acting as a CFHT test bed for KIR support and away from being tied to a specific observing run.
The camera contract with the University of Hawaii was signed in mid July. We currently expect the system to be available for population with CCD's by February 1997. We have also entered into a shared cost development with Gerry Luppino on software development for a 2nd generation SDSU controller. This controller will allow for greater readout speed and, as a bonus, will give us 12 analog channels. There is room inside the dewar for twelve devices. If we can acquire twelve devices we will install all of them on the focal plane.
The camera design has been upgraded with the addition of chip mounts and ccd's for potential in-dewar autoguiding. Electronics and control for such a guider facility have not been addressed.
The S-Buss interfaces for the project have been delivered and are being used at CFHT to support the UH 8k camera. The interfaces are working well.
We have decided to continue the current loan agreement with Gordon Walker at UBC indefinitely since development of this device as a CFHT project is not in our current planning, and since Gordon points out that there are some concerns about the long term life of the devices. The project for development of a dual array camera holding one thinned and one thick device has been put on hold pending operational commissioning of 2 more thinned 2k square devices.
Loral 5 is the next thinned ccd awaiting commissioning. The device, mounted in a dewar, was delivered by Gerry Luppino two weeks ago.
The OSIS IR camera, given high priority by the SAC, has progressed moderately. We entered into a purchase agreement with Rockwell at the beginning of August. Since then we have had discussions with University of Montreal regarding development of the camera. We have started development of the contract and technical specifications, but do not at the moment have a clear date for completion.
A preliminary version of this software has been implemented for both the BEAR mode of RedeyeW and for the KIR camera. This software replaces much of the old, problematic acquisition system with a more streamlined system which uses VME memory in the host computer. We have had preliminary design reviews on this system and hope to implement the software on all CCD and infrared camera systems as soon as possible.
This device is officially dead. Mike Lesser, University of Arizona, was unable to remove the contamination from the surface of the device after the anti-reflection coatings were removed. It remains unknown exactly how the contamination was acquired.
These CCD host computers have been upgraded with new software and hardware and are configured to be identical. Cassini has been shipped to OMP in France. Both hosts now have the Chrislin VME memory and 4 GByte hard drives for local image storage. The prototype GenIII V4 software has been installed on both systems. Continued software development will take place on Titan at CFHT headquarters.
The software group has put a major effort into the organization and improvements of the Waimea Network. Two high-speed ethernet switches and hubs, were installed to provide rapid access to a central data server for data reduction available for resident astronomers and visitors. Network cabling was upgraded to category 5 twisted pairs cables in the computer room and the staff astronomers offices to support 100 Mbits/sec data rate.An ultra sparc 2 with 512 Mbytes of memory and a battery of high performance, high capacity disks are presently under installation. To facilitate the processing of large format CCD mosaic data, high resolution display (1600x1200) Xterminals were acquired and received to replace the present sparc 5 workstation used by the staff astronomers.
The summit network bandwidth is being upgraded to support a 100 Mbits/sec rate among all the data acquisition and instrument control computers (HPs and SUNs). This was deemed necessary to facilitate the data handling of present and near future large CCD mosaics.
Integration of the UH8K CCD Mosaic was done using an upgraded Sparc 20 with 512 Mbytes of memory and a 2 9 Gbytes disks. A preliminary scheme for data archiving was also installed and tested.An additional Ultra Sparc 2 with 2 processors, 512 Mbytes of memory and a 36 Mbytes RAID disk has been purchased to provide facilities for local processing of the data acquired.
Other developments include the migration of the CFHT data logger to an HPIB server connected directly to the net. Data logger data are now recorded at 10 minute and 30 second interval with the 30 second data stored in a scaled integer format.
The data archive optical disk failed this semester and has been replaced by Exabyte tape. We plan to remain with Exabyte tape until new high density CD rom technology is available, hopefully sometime in the new year.
Other major efforts such as AOB and GenIII v 4 development are touched on under individual projects.
Although PCS are not required for operating the observatory, they have become a part of every employee's set of tools here at CFHT. With over 40 PCS connected to the Waimea and Observatory local-area networks at last count, keeping them functioning has been time consuming. Hardware failures, persistent software problems and software driven upgrades have been the major reasons why support is required. Supporting the PCS consumes one technician at least half-time.
Initial on-sky tests using a TCS IV control loop in mid June were very successful. The process showed the effect of Declination creep with HA as result of Dec encoder interactions with structural flexure of telescope. Switching the TCS IV in and out took roughly 5 minutes each way. A further single daytime set of dome-closed tests was used to characterize incremental vs absolute encoder responses. The resulting data have helped clarify the rather complex relation between these data sources.
As part of the TCS -IV design process, a set of forum meetings between the TCS and Software groups explored options for data connections between data acquisition systems and the TCS.
An initial (updated and consolidated) version of the TCS IV software system design notebook was issued inside the TCS-IV group. The document is the touchstone for future developments and implementations.
A TCS IV design review with 3 external referees and several in-house staff in October provided a useful reference on what we are doing and how well we are doing it. At this writing the summary report from the referees has not been received, but in summary they don't feel that we are doing anything greatly wrong, but have several good suggestions worth considering for the direction and focus of the project.
Apart from the specific items listed above which are included in the New Imaging Plan, the following actions have taken place.
A meeting between CEA project staff and Waimea management/engineers took place in Waimea in late September. Discussions included an exploration of the scope of the project and initial agreements on which agency would take responsibility for the various parts of the project. Details are included in a separate presentation by O.Boulade.
In response to SAC's request at the May, 1996 meeting, CFHT engaged several optical designers to provide initial designs and costing estimates for a Prime Focus Wide Field Corrector capable of producing excellent image quality over a 1.4 field. The results of the feasibility study have been forwarded to SAC under separate cover. In brief, there appears to be no problem at the design level. However, as expected, such a corrector will be expensive ($1 to $1.3M US) and will require a major rebuild of the Prime Focus Environment.
Costing for the rebuilding of the Prime Focus Environment was handled separately with the Canadian firm ASA, located just outside Victoria B.C. Since this study was instigated only after the range of likely prime focus corrector designs became clear, the study results will be arriving at CFHT only just by the start of the upcoming SAC meeting. However, given the scale of the most promising optical design, the scale of required PF environment rebuilds will be large, with little of the existing equipment likely to be used.
Staff safety has been an issue which has been addressed with considerable effort this semester. In brief, safety actions have included :
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The SAC is pleased with the progress that has been made on the 8K x 10K detector. We agree that it is desirable to increase the size to 8K x 12K if this can be done within the present dewar at little additional expense. There is some concern about the poor blue response reported for the Lincoln-Labs CCDs. In the selection of individual CCDs for the camera, better blue response should be a principal consideration. We also emphasize the importance of rapid readout of the array, in order to minimize the overhead associated with use of the detector. It is important that the camera be available for use by the community as soon as possible and not later than semester 98-I.
Since the last SAC meeting, CFHT has investigated designs and rough costs for larger field correctors, as requested, and the Megacam consortium has presented camera designs to use this field. The consortium has clarified its science proposals, held detailed briefings at CFHT and DAO, and requested independent funding of a data-processing pipeline. The SAC has reviewed these developments and invited L. Vigroux to its recent meeting. Based on rough costs estimates, the SAC presents the following priorities for wide field imaging at CFHT:
SAC confirms its view that wide field optical imaging remains its top priority to use the telescope most effectively in the mid-term future. We note that we regard all of the following as essential elements.
1) A uniquely wide field with excellent imaging. This means a field of about one square degree or more, with tip-tilt correction, atmospheric dispersion correction (ADC), and wavelength coverage to 3800A or lower.
2) An efficient observing and data-logging system. This means rapid readout (less than 30 seconds), automatic focussing, and efficient guide-star acquisition.
3) The use of the camera for major scientific programs to be planned and shared by the CFH user community.
4) An efficient and rapid data-processing pipeline, making the results widely available on a short timescale.
We regard the wide-field Megacam as our preferred option for achieving all these.
We realise that enlarging the wide field corrector (WFC) is a major and expensive part of this plan. Thus, we recommend that the full extent of the circular field be sampled with CCDs, as this will constitute a major advantage and use of investment. We urge that funding be sought to accomplish this goal. We also offer the following as likely ways to achieve some economies.
1) Investigation of the cost tradeoffs among all three optical design options, particularly in image quality and ADC implementation.
2) Investigation of designs that use the final optical element as the camera window.
We consider that the 13.5 micron pixel size available as one option, is preferable in sampling the images. This should be a consideration in all designs. The SAC wishes to be informed and involved as these studies progress.
In the event that the larger WFC cannot be funded, we recommend as second option a descoped camera, which will maximise the field without major prime-focus environment work. This will still require new optics, tip-tilt, and ADC, but should incur much less costly changes. In this option, we note that image quality, efficient operations, and data-pipeline are unaltered essentials. We also note that filling the available field with CCDs will still afford a large margin over any other camera, and still allow major imaging programs of the type envisaged, although they would have to be descoped.
In the event that a descoped Megacam cannot be achieved, as third option we recommend making use of the planned '12K' camera in a similar fashion. This implies WFC upgrade, rapid readout, and data pipeline as before, but the latter would have to be achieved without the expertise and resources of the Megacam team.
We regard the scientific operations of the camera as important. To achieve its potential, large scientific programs must be undertaken, using an appreciable fraction of observing time. These programs must be planned and carried out by the combined scientific communities, and available to all. The Megacam proposed programs are very exciting but need to be planned and refined by a joint activity. We strongly suggest that this be initiated at a workshop early in 1997, involving scientists from all three communities. We note that the scientific communities need to strike a good balance between the efficiencies and major science goals of joint programs, and the ability to continue individual proposal-driven investigations. We feel that this change in mode of operation of CFHT is natural and desirable, and will make the best use of the telescope during the 8-metre telescope era.
The SAC reaffirms the high scientific importance of wide-field imaging in the infrared. We believe that the current participation of CFHT in a consortium to develop 2K x 2K infrared CCDs is an appropriate way to proceed. Because it is expected that several years will be required to develop successful devices, further action is not needed at this time.
CFHT and Lyon teams are presently working on the acceptance phase of the instrument which includes acceptance tests and acceptance document. CFHT staff plans to go to Lyon in November 96 for an intermediate phase of this process and mechanical tests at OHP are planned in December 96. The final acceptance is foreseen at CFH in Spring 97.
A draft of the contract between CFHT and OASIS team is in preparation defining the status of the instrument. After compliance with CFHT requirements, OASIS will be a CFH guest instrument for a duration of at least 5 years. Concern has been expressed on the use of the data software for non-expert observers. SAC stressed that the avaibility of a user-friendly software must be part of the final acceptance of the instrument. SAC suggests that commissioning time will be open in semester 97-2 to some OASIS users in order to test such an avaibility.
If all the tests are succesfull, OASIS will be offered to the whole CFH community in semester 98-1.
Preamble:
After encouragement to proceed given by SAC in May 96, the proponents of this project continued their study of a fiber link between the AOB and OSIS, and raised some money. However, it was not clear whether or not the SAC recommendation to study the possibility of direct coupling at f/8 was really investigated. In addition of providing larger fields at f/8 on seeing limited images, such a possibility would also allow intermediate samplings between the AO corrected images and the seeing limited ones. On the technical side, this may require microlens coupling at both input and output ends of the fiber link. At 0.1 arcsec/fiber and high spectral resolution, only few extended objects will be bright enough to be observed, and versatility in spatial sampling is a mandatory requirement to provide a wider range of applications.
In consequence, the SAC wishes to make the following recommendation:
The SAC reiterates the scientific merit of providing a fiber link between the f/20 AOB and the OSIS spectrograph. The SAC strongly reaffirms that versatility in spatial sampling and field coverage shall be provided, if feasible, to significantly enhance the scientific value of this fiber link. A detailed study of alternative designs and of their performances is requested by SAC for further evaluation. In order not to slow down the development of this project, the SAC has appointed Jean-Gabriel Cuby to act as a continuing liaison and report to the SAC.
A project for a spectropolarimeter at CFHT was presented to SAC by J.-F. Donati and C. Catala. This instrument would include a polarimeter capable of performing both circular and linear polarization analysis, and an echelle spectrograph with cross-dispersion, providing a complete coverage of the visible domain (380nm - 1 micron) in one single exposure, at a resolving power of 50,000. Such an instrument would be needed in its polarimetric mode for the study of stellar magnetism and of stellar circumstellar envelopes, and would be unique in the world in this configuration. In its classical spectroscopic mode, this instrument would be used for example to study stellar rotation, stellar surface inhomogeneities, stellar pulsations, chemical abundances, as well as stellar accretion disks and winds. This instrument would compete efficiently with the echelle spectrographs of the 8-10m telescopes, for all scientific programs taking full advantage of the large multiplex gain provided by its wide spectral coverage.
After hearing the presentation of this instrument, the SAC discussed its scientific objectives, and wishes to make the following recommendation:
Considering that this instrument will be unique in the world; considering that this instrument provides more opportunities for research than the current Coude spectrograph; considering that this instrument will provide an excellent use of CFHT bright time; considering that many members of all three communities (about 30) have expressed support for its construction; The SAC recognizes that the spectropolarimeter proposed by Donati and Catala has high scientific merit. The SAC therefore supports the development of this instrument and its inclusion in the instrumentation plan if money is available beyond that committed to the other projects.
Shortly after the May 1996 meeting of SAC, the composition of the Ad Hoc Sub-Committee on the `Long-Term Future of the CFHT' was finalised. France was to be represented by Guy Monnet and Daniel Rouan; Canada by Jean-Rene Roy and Doug Welch; and Hawaii by Bob McLaren. The committee, under the Chairmanship of SAC member David Hanes, scheduled a first meeting at the CFHT in late September 1996. As an important preliminary, the Chair and various committee members spent some time in Email discussions, principally with CFHT Director Pierre Couturier, over the exact terms of reference and the mandate of the committee. Eventually an understanding was reached with the Director over the clear distinction to be drawn between mid-term and long-term planning. The committee agreed to meet under the terms of reference as they had been drafted by Pierre Couturier and Harvey Richer, the outgoing SAC Chair. (A copy of those terms of references, complete with explanatory comments added by Messrs Couturier and Richer, is attached as Appendix 1.)
The Committee, with the exception of Guy Monnet, who had other unavoidable commitments, met at CFHT headquarters on Friday 20 September and Saturday 21 September and enjoyed very stimulating discussions, many of which were also attended by Pierre Couturier, Derrick Salmon, and Dennis Crabtree (all of whom provided important and useful technical and background information). A copy of the Committee's one-page report is attached as Appendix 2; additional brief remarks follow here.
The Committee noted that there was no reference in the explicit terms of reference to a conversion of the present telescope to a new Cassegrain configuration (such as the f/16 option raised by D. Crampton at the Lyon meeting), although there are allusions to it in the added comments. At an early stage, however, the Committee ruled out such an option as a long-term objective. Moreover, the Committee was likewise unenthusiastic about proposals which entailed replacing the telescope with one of somewhat larger but still moderate size (by the time of construction, a decade from now). The Committee felt that the excellence of the site - perhaps the best in the world - and the pre-existing body of technical expertise, astronomical experience, and political cooperation represented by the CFHT demanded that a more ambitious and worthy enterprise be considered.
For varied technical reasons (the present limitations of fabrication, the physical plant available in the CFHT dome, and so forth) is was deemed unlikely that a monolithic mirror very much larger than Gemini-sized could be accommodated within the present structure. The Committee recognized, however, that segmented-mirror technology is now of proven feasibility, and anticipates that a decade's experience of telescopes designed in this way should yield the improved technical understanding which will permit their extension to significantly larger apertures. Moreover, information provided to the Committee suggested that the present CFHT dome might provide the basic structure adequate to the support of such a redesigned and much-enlarged CFH Telescope, permitting the construction of (perhaps) the world's largest telescope, and ideally its finest, at a great saving in total cost.
As the initial step in this direction, the Committee prepared a first brief report (attached as Appendix 2). This report, submitted to the CFHT Executive, requested that preliminary engineering estimates be commissioned to explore the potential of the present CFHT building for the larger facility. Furthering the project, if it is indeed eventually deemed feasible, will require the preparation of a strong scientific case; Committee members Hanes and Welch undertook to start the development of such a case. In the longer term, as was recognized in the original terms of reference, it will also be necessary to consider the astronomical needs and capabilities of the partners (Canada, France, Hawaii) in the post-Gemini, post-VLT era if such a development is to be supported.
By the time of the SAC meeting in November 1996, no engineering assessments were available.
During the months separating the biannual SAC meetings, little contact occurs between the SAC members or between them and the executive of CFHT. The implementation of the instrumentation plan brings the necessity of more frequent interaction and discussion between the aforementioned parties. Advice will have to be given frequently and promptly to increase the efficiency of the implementation.
Therefore, the SAC recommends that discussions take place between the executive and the SAC members every three months via e-mail or teleconference. The executive will provide status reports on a limited number of subjects related to the instrumentation plan in order to assure prompt decision making. This recommendation does not overide the necessity of the SAC members physically meeting every six months during these critical years.
Late in 1996, CFHT will be offered a high-bandwidth connection from their Kamuela headquarters to the summit. This is a fiber-optic connection and will replace the present T-1 (1.544 Mbit/sec) connection. The SAC was informed that CFHT will acquire a DS-3 (45 Mbit/sec) connection (higher bandwidth is also available but at a higher monthly charge). With the advent of this high-bandwidth connection, the possibility of remote observing was briefly discussed. Remote observing has become routine at Keck, and is now the usual operating mode for their most simple/reliable instrument (HIRES); remote operation of the Keck telescopes will become more common in the future. However, Keck has on-site dormitories, whereas CFHT does not. The hotel facilities in Kamuela do not seem to be practical for daytime sleeping. The Director pointed out that for safety, two people would need to be at the telescope, and therefore expected that remote observing would likely increase the operating cost (Keck does not have this problem because they have two telescopes and an operator at each).
As part of the hardware for the DS-3 connection, CFHT has the option of purchasing equipment to enable a bidirectional audio/video link between the summit and Kamuela. The SAC was informed that this was already planned. This link will facilitate better summit/headquarters communication, better troubleshooting, and permit some preliminary experiments in remote observing.
John Tonry (UH-Institute for Astronomy) and Barry Burke (MIT Lincoln Laboratory) have developed a CCD capable of rapidly and noiselessly transferring charge in all four directions. This permits image motion compensation to be performed on the detector electronically, rather than using mechanical means such as a rapidly moving secondary or tertiary mirror.
Devices measuring 512 x 512 OTCCD area with adjacent 512 x 512 three-phase area (used for the guide stars) have now been constructed and tested at Kitt Peak. An improvement of image quality of approximately 0.2" FWHM was typically achieved. The main problem with these OTCCDs are charge pockets---these leave holes in the OT tracked image. More experimentation is needed to reduce the incidence and effect of these pockets.
These OTCCDs appear to be very relevant to the high-resolution and wide-field imaging goals of the CFHT, and the development of these CCDs should be watched closely. John Tonry has offered to lend one of these CCDs to CFHT for testing. There has not yet been any test of OTCCDs on Mauna Kea. It will be interesting to compare tests of an OTCCD on the UH 2.2-meter telescope (which has optics capable of producing images with FWHM <0.2", but has poorer thermal control of the dome and more dome seeing than CFHT) with the CFHT (where the primary mirror figure is not as good, but there is less dome/telescope seeing).
The Keck Observatory has submitted a proposal to the Director of the Institute for Astronomy requesting permission to operate a laser (589 nm wavelength, 25 Watts emitted power) attached to the side of the Keck II telescope. This laser will be used to produce an artificial guide star of approximately 9th magnitude in the sodium layer (approximately 90km altitude).
The major impact on other observatories does not appear to be seeing the guide star itself (collisions are unlikely), but collisions with Rayleigh scattering in the beam from dust and aerosols at altitudes up to about 10km above the summit.
There is a potentially major impact on CFHT because of the wide-field imaging carried out with CFHT---the CFHT beam expands to a large size (1 degree square corresponds to 40 x 40 meters) at a typical collision altitude of 2km, significantly increasing the collision frequency relative to narrow field/point source observations. The major impact is on the V and R-bands, both of which include the sodium wavelength.
Keck used a Monte Carlo simulation to estimate that with zero field of view and random pointing with 1 hour exposures, CFHT would experience 0.2 collisions per 10 hours. With the larger field of view, this increased to 0.4 collisions per 10 hours, with each collision lasting longer. A further simulation restricted both telescopes to a region within 15 degrees of the NGP, and yielded 2.4 collisions per 10 hours. This last simulation is regarded as being the most worrisome, and perhaps the most realistic, because on any given night, telescopes are not pointed randomly---for example in March/April, most observations in dark time are extragalactic on CFHT and the Keck telescopes, and concentrated towards the Galactic pole. Keck is proposing to monitor pointing information from all Mauna Kea telescopes, and shutter the laser before a collision occurs. A working group has been established to further evaluate the laser guide star proposal, and to propose a policy for laser guide stars on Mauna Kea. This group will consist of one representative from each of Keck, CFHT, Subaru, Gemini, and the UH 2.2-meter telescope. In this group, Subaru, Gemini, and perhaps CFHT may be interested in pursuing laser guide stars in the future, but in the shorter term plan to use natural guide stars. Because of its proximity, laser guide stars at Gemini will have the most impact on CFHT. The IR telescopes on Mauna Kea are less impacted by this proposal, so will not actively participate in this group.
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The CFHT refereed publications database is a reality. In 1983, Liz Bryson and then,Executive Director, Dr. Gerard Lelievre, initiated a project collating and summarizing data from CFHT refereed papers. The information was installed on d-Base II. Unfortunately, this project was abandoned until Dr. Pierre Couturier expressed interest in its revival, primarily due to a paper published by Virginia Trimble entitled, "Papers and Citation Resulting from Data Collected at Large, American Optical Telescopes," which appeared in PASP, 107, 977. Dr. Trimble's assertions, based solely on North American publications, placed CFHT as sixth in citation productivity amongst the leading observatories, in spite of the fact that 45% of CFHT's papers are published in European journals. Thus, in response to her paper,as well as the growing need to accurately evaluate observers' request forms, we set out to reassess CFHT's paper productivity from the years 1992-1994. Liz acquired the CFHT information from three sources: 1. CFHT pre/reprints, 2. Personal scanning of all major journals, and 3. Observers' request forms. Following her perusal of the aforementioned documents, Dr. Marc Azzopardi fine-tuned the project by citing off-shoot writings and designating instrumentation, focus, and key words of the articles. Dr. David Bohlender designed the database with the use of the PC software program, Access, which enables one to access statistics regarding publications as they relate to focus, instrument, journal, keyword, author, and number of citations. The project will be adding the year 1995 and eventually including the years prior to 1992. The value of such a database will not only enable the Executive a critical analyses of CFHT's publications but also perhaps enable the corporation to exchange this information with Insitute for Scientific Information and the Canadian Astronomical Data Centre for use by the greater astronomical community.
Both TACs are well aware of the recommendation about key programs. Some kind of key projects have already been approved. A better information of the community about the welcome of such projects remains to be done.
As of January 1st, 1997, Paul Hickson will replace Gilles Joncas, and Pierre-Olivier Lagage will replace Claude Catala on the TAC. The SAC thanks Gilles and Claude for their work on this committee.
In case the present frequency of the SAC meetings is maintained, the next SAC meeting will be held in Toulouse, on 15, 16, and 17 May, 1997. The TAC meeting will be on 15 May evening. If the frequency of the SAC meetings is reduced to once a year in 1997, then the next SAC meeting will be held in Waimea, on Oct. 30, 31, and Nov. 1, 1997. The next teleconference or email SAC discussion will take place during the sixth week of 1997, between February 4 and 7. The agenda of this email or telephone contact will be circulated later.
At the 55th meeting of the Board of CFHT, the Board "asked SAC to form a small working group to examine, for the long term evolution of CFHT, the technical feasibility of a 6-8 meter mirror possibly within the existing dome." SAC appointed David Hanes to chair this working group.
The terms of reference for this working group are as follows:
(a) to interact (likely via email) to establish a scientific case for such an instrument, specifically the case for a new telescope and its associated first generation instrumentation, taking into account the access given to the three communities via Gemini (Canada), VLT (France) and the Mauna Kea telescopes (UH).
(b) to consult with professional engineers and others as required to establish the parameters for such a telescope (eg design and aperture that will fit into the existing dome). The main questions which will have to be explored with these technical studies are:
1/ the cost of removing the present telescope from the dome and possibly dismantling the dome itself.
2/ the cost of inserting a new telescope mounting (with or without The present dome).
3/ one important question which will have to be analyzed if the project is to proceed is the reshaping of the Corporation: staffing plan, starting a project group, recreating a group for operation. The total cost and scheduling of this plan has to be part of the whole project since it has significant financial impact.
4/ not totally independent of the previous question is the problem of whether or not to introduce new partners.
(c) CFHT is expected to cover reasonable costs associated with this exercise.
(d) together with (a) and (b) above to decide if the project should be pursued.
(e) if the project is to proceed, to identify in both Canada and France a champion for the project.
(f) the working group will report its term of reference initially to SAC and the Committee of the Board meeting in May.
It is the opinion of this committee that recent advances in optical and infrared astronomy have been primarily the consequence of improved capabilities in angular resolution, light-gathering power and the ability to conduct observations in non-traditional wavelength regimes. While the CFHT has served its users well by setting the technical standard in these areas, we believe that the *long-term* (i.e. starting 2005) facility needs of the three communities would be best served by replacing the existing 3.6m telescope with a segmented mirror instrument of 12-16m aperture on the same site (possibly using the same pier). In comparison with Keck, such a telescope would provide a 50% increase in resolving power in the 3-5 um regime and would allow the deepest and most detailed imaging of high-z objects and star-forming regions. It would also provide a doubling of light-gathering area over the largest existing telescopes at all wavelengths.
In a subsequent report, we will describe in more detail why we feel that a 6-8m class replacement or instrumentation/focal ratio upgrade would not be competitive or desirable on a 10-year timescale and how our proposed replacement adds value to the joint community assets (which at that time will be at least six 8m facilities) at a fraction of the cost of developing the same telescope from scratch.
We request that short-term technical studies be initiated to explore the feasibility of installing a 12-16m segmented mirror telescope on the existing site. Specifically, these studies should:
1) identify the largest telescope which could reasonably be installed making use of the existing pier.
2) identify the factors which lead to this size limit.
3) produce a preliminary costing of such a facility and establish the salvage value of selected components.
4) estimate the shutdown time required to rework the summit facility.