Dear AASTOWG member, Please find attached the draft minutes for the meeting we had in Canberra on 1 April 1995. At this stage I am only distributing the minutes to the members of the AASTOWG as constituted in March 1994, but plan to distribute it more widely (to at least all the attendees of the 1 April meeting) after I receive any comments that you may have. Regards, Michael (Ashley) Your action items: 1 - Read this message! 2 - Send me any additions/corrections (I am particularly interested in refining the lists of people in the various sub-project groups; if you know of researchers in other disciplines (e.g., atmospheric sciences) who would be interested in the AASTO data, please let me know). 3 - Go build your instrument! ------------------------------------------------------------------------------- CONTENTS 1 - List of attendees and other associated people. 2 - Comments on electronic communication within the AASTO project. 3 - List of e-mail aliases, suitable for your UNIX .mailrc file. 4 - Minutes of the 1 April 1995 meeting. 5 - History of the AASTO project. 6 - Timeline for deployment of AASTO. ------------------------------------------------------------------------------- Attendees at second AASTOWG meeting (1 April 1995, Mt Stromlo Observatory, Canberra, Australia): *Michael Ashley (co-chair) mcba@newt.phys.unsw.edu.au UNSW *John Bally (co-chair) bally@nebula.colorado.edu U. Colorado Michael Burton mgb@newt.phys.unsw.edu.au UNSW Sean Casey sean@irastro.gsfc.nasa.gov Goddard SFC *Jack Doolittle doolittle@agena.space.lockheed.com Lockheed *Mike Dopita Michael.Dopita@anu.edu.au ANU Al Harper al@oddjob.uchicago.edu Yerkes Gary Hovey hovey@mso.anu.edu.au ANU *Bob Loewenstein rfl@yerkes.uchicago.edu Yerkes *Jeff Peterson jeff@cmbr.phys.cmu.edu Carnegie Mellon *Bob Pernic pernic@yerkes.uchicago.edu Yerkes Bernie Rauscher bjr@oddjob.uchicago.edu U. Chicago Joe Rottman joe@obbjob.uchicago.edu ASA John Storey jwvs@newt.phys.unsw.edu.au UNSW Jim Sweitzer jss@oddjob.uchicago.edu Yerkes Jean Vernin vernin@ayalga.unice.fr U. Nice, France * = member of the AASTOWG as established in March 1994. Apologies (members who couldn't attend): *Peter Hall phall@atnf.csiro.au ATNF *Tony Stark aas@cfa.harvard.edu CfA (AST/RO) Additional people who attended the first meeting in 1994, or who are on John Bally's e-mail list for the first meeting minutes, or who have relevant expertise (if anyone can fill in the missing e-mail addresses and institutional affiliations, it would be appreciated): Pierre Bely bely@stsci.edu STScI/JHU Jousef Billawala Uni. of Colorado Richard Chamberlin Boston U Dick McCray dick@jila.colorado.edu Frank Bartko fbartko@cass157.colorado.edu CASA David Fischer ASA Holland Ford ford@jhufos.pha.jhu.edu Ed Friedman Ball Aerospace Jay Tilly jtilly@ball.com Ball Aerospace Simon Radford sradford@heineken.tuc.nrao.edu NRAO Dave Theil U. Colorado Companies that may have relevant technology (this list is in its very early stages, we need fax/phone/email data and info on what expertise the company has): Schaeffer Magnetics Space Data Bendex Compumotor ------------------------------------------------------------------------------- There are several ways to facilitate electronic communication between the various people involved in the AASTO project. Here are some possibilities, with pros and cons: Idea Pros Cons ----------------------- --------------------- --------------------------- Each person has his/her Simple to set up Difficult to keep everyones own e-mail list lists in synch An e-mail exploder Keeps lists in synch Can generate large amounts of noise Allows subscription/ Requires each person de-subscription easily to maintain an archive USENET news Archives all messages Not everyone is in the at a central location habit of reading news You only read what you If you don't make the effort are interested in. to read news frequently, you will not see messages in a timely fashion The World Wide Web Easy to use Not immediately applicable to discussions A hardcopy newsletter Easy to use Slow Not appropriate for discussions What I propose to do initially is to send out a list of e-mail aliases for the various sub-projects within AASTO (this list begins below), and then to set up a special newsgroup hierarchy for AASTO (probably starting at unsw.physics.aasto), which people could try out. Note that USENET news can be read from within most Web readers. I will establish an AASTO Web page http::/www.phys.unsw.edu.au/~mcba/aasto with pointers to the various projects, and with the most recent version of this e-mail list. I will distribute a newsletter (possibly associated with ``Looking South'', the newsletter of the Australian Working Group on Antarctic Astronomy). # Cut here and add to your .mailrc file if you wish. Lines starting # with a hash symbol ``#'' are comments, and are ignored by the UNIX mail # program. Lines ending with a backslash (with no trailing blanks) are # continued on the next line. # alias michael_ashley mcba@newt.phys.unsw.edu.au alias john_bally bally@nebula.colorado.edu alias frank_bartko fbartko@cass157.colorado.edu alias pierre_bely bely@stsci.edu alias ian_bourne UNKNOWN alias michael_burton mgb@newt.phys.unsw.edu.au alias sean_casey sean@irastro.gsfc.nasa.gov alias jack_doolittle doolittle@agena.space.lockheed.com alias mike_dopita Michael.Dopita@anu.edu.au alias holland_ford ford@jhufos.pha.jhu.edu alias peter_hall phall@atnf.csiro.au alias al_harper al@oddjob.uchicago.edu alias mark_hereld hereld@bucephalus.uchicago.edu alias gary_hovey hovey@mso.anu.edu.au alias bob_loewenstein rfl@yerkes.uchicago.edu alias rodney_marks rdm@newt.phys.unsw.edu.au alias dick_mccray dick@jila.colorado.edu alias fred_mrozek mrozek@bucephalus.uchicago.edu alias bob_pernic pernic@yerkes.uchicago.edu alias jeff_peterson jeff@cmbr.phys.cmu.edu alias simon_radford sradford@heineken.tuc.nrao.edu alias bernie_rauscher bjr@oddjob.uchicago.edu alias joe_rottman joe@obbjob.uchicago.edu alias tony_stark aas@cfa.harvard.edu alias john_storey jwvs@newt.phys.unsw.edu.au alias jim_sweitzer jss@oddjob.uchicago.edu alias david_theil UNKNOWN alias jay_tilly jtilly@ball.com alias jean_vernin vernin@ayalga.unice.fr # # Here are the original members of the AASTOWG: # alias aastowg michael_ashley john_bally jack_doolittle mike_dopita \ peter_hall bob_loewenstein jeff_peterson bob_pernic tony_stark # # Here are the Principal Investigators for the various instruments: # alias aastopi michael_ashley john_bally ian_bourne jack_doolittle mike_dopita \ mark_dragovan gary_hovey bob_loewenstein jeff_peterson \ bob_pernic john_storey jean_vernin # # Here is everyone who appears in any of the sub-project interest groups # at the end of this file: # alias aastoeveryone aastopi peter_hall mark_hereld rodney_marks fred_mrozek \ bernie_rauscher tony_stark # # Here are some aliases which could be used to e-mail people who have # expressed interest in the various sub-projects within the AASTO # project. The first person in each list is the Principal Investigator # for the sub-project, as recommended at the 2nd AASTOWG meeting # (these assignments are not cast in stone). The remaining people are # those that I (M. Ashley) judged to have an interest in the # sub-project on the basis of comments at the 2nd AASTOWG meeting. # Please let me know of any additions/corrections to this list. # # If you are interested in a sub-project, and you are not on the list, please # let me know so that I can add your name. # # The alias names have a dot (``.'') in them so that they are # identical to the trailing part of the corresponding USENET newsgroup. # All the aliases include an address at ``newt.phys.unsw.edu.au'' which # can be set up to automatically post any incoming messages to the # desired newgroup. # # Here is an example of using one of these aliases: suppose that # you wanted to e-mail everyone who had an interest in the generic mounting # sub-project, then on a UNIX system you could type # # mail aasto.mount # # The sub-projects are listed in alphabetical order. # # AURORA - the auroral all-sky camera experiment. # alias aasto.aurora jack_doolittle aastoa@newt.phys.unsw.edu.au \ michael_ashley bob_loewenstein # # COM - aspects of communication to/from the AASTO. # alias aasto.com bob_loewenstein aastoc@newt.phys.unsw.edu.au \ michael_ashley jack_doolittle # # DIMM - the DIMM (Differenetial Image Motion Monitor) experiment. # alias aasto.dimm mike_dopita aastod@newt.phys.unsw.edu.au \ michael_ashley john_bally michael_burton gary_hovey bob_loewenstein \ rodney_marks jeff_peterson john_storey david_theil # # FTS - the possible mid-IR Fourier Transform Spectrometer experiment. # alias aasto.fts mark_dragovan aastof@newt.phys.unsw.edu.au \ michael_ashley john_storey # # MICROT - the microthermal air-turbulence experiment. # alias aasto.microt jean_vernin aastot@newt.phys.unsw.edu.au \ michael_ashley michael_burton rodney_marks john_storey # # MOUNT - the ``generic mounting'' which is to be used to point # and track various instruments. # alias aasto.mount gary_hovey aastom@newt.phys.unsw.edu.au \ michael_ashley fred_mrozek bob_pernic jeff_peterson \ john_storey # # NEARIR - the near-infrared photoemeter (spectrometer?) experiment # alias aasto.nearir michael_ashley aaston@newt.phys.unsw.edu.au \ michael_burton mark_hereld bernie_rauscher # # POWER - the whole question of power supplies and batteries for # the AASTO. # alias aasto.power michael_ashley aastop@newt.phys.unsw.edu.au \ jack_doolittle gary_hovey john_storey # # ROCKET - the possible use of rocket sondes to launch small experiments. # alias aasto.rocket john_bally aastor@newt.phys.unsw.edu.au \ michael_ashley john_bally jack_doolittle john_storey # # SKYHOOK - discussions of towers, balloons, etc. Basically any # mechanism for placing sensors or sources (e.g., for an # artificial star for the DIMM) above the ground. # alias aasto.skyhook bob_pernic aastoy@newt.phys.unsw.edu.au \ michael_ashley john_bally jack_doolittle mike_dopita fred_mrozek # # SOUNDER - the acoustic sounder experiment. This depends on feasibility. # alias aasto.sounder ian_bourne aastos@newt.phys.unsw.edu.au \ michael_ashley jack_doolittle # # SUBMM - the sub-millimetre experiment. # alias aasto.submm jeff_peterson aastob@newt.phys.unsw.edu.au \ michael_ashley john_bally peter_hall tony_stark john_storey # # UVVIS - the UV/visible spectrometer experiment. # alias aasto.uvvis john_storey aastou@newt.phys.unsw.edu.au \ michael_ashley michael_burton jack_doolittle mike_dopita gary_hovey \ rodney_marks ------------------------------------------------------------------------------- Minutes of the 2nd AASTOWG meeting (1 April 1995, Mt Stromlo Observatory, Canberra, Australia): Note: some material has been added in addition to that presented at the meeting. This is shown in the text by inclusion within ``(*** ***)''. Contents: 1. List of documents distributed at the meeting. 2. Instruments in order of increasing wavelength: - UV/visible spectrometer. - Auroral all-sky camera. - DIMM. - Near-IR. - Mid-IR. - Far-infrared Fourier Transform Spectrometer (FTS). - Sub-mm bolometric tipper. 3. Non-electromagnetic instruments: - Microthermal measurements. - Scintillometer. - Acoustic sounder. - Ceileometer. 4. Other instrumental consideration: - Duty cycle of the AASTO. - Alternative power sources for the AASTO. - Power supply issues. - Communications. - Generic mounting. - Lockheed star-tracker. - Heat pipes. - Transparent domes. - Rocket sonde. - UNSW Antarctic Test Facility. 5. Deployment of the AASTO. 6. Next meeting. Documents distributed: - Agenda - Comments from Peter Hall on ATNF's proposed contributions - Strawman Statement of Work from Jack Doolittle, 21 March 95 - Gary Hovey's DIMM document - Four viewgraphs from John Storey's talk on the AASTO program UV/visible spectrometer: John Storey discussed the proposal for UNSW to contribute a UV/visible spectrometer. The following text is taken from an article in press in Publications of the Astronomical Society of Australia (PASA). This experiment will monitor the atmospheric transmission from 300 to 1100 nm, and will also allow an assessment of the significance of the auroral emission lines throughout this range. Because there is negligible atmospheric thermal emission at these wavelengths, the atmospheric transmission must be measured directly by taking spectra of bright stars with a small telescope. Initially, we will construct a simple prime-focus instrument with a 20 cm diameter primary mirror. At the focus we will mount a group of 100 micron diameter optical fibres, each defining a field of view of 1.2 arcminutes. These fibres direct the light back to the AASTO where a spectrometer with a passively cooled CCD array will cover the UV/visible region at a resolution of approximately 1 nm. With bright stars such as Beta Centauri and Fomalhaut an integration time of a few tens of seconds is all that is necessary to achieve adequate photon statistics. The large field of view of each fibre also results in good sensitivity to airglow and auroral emission, receiving the same flux as a 0.5 arcsecond pixel would on a 7 metre diameter telescope. A prototype of this instrument will be built with funding from the Australian Antarctic Foundation and a small ARC grant during 1995, then followed with an upgraded instrument with a 30 cm lightweight metal mirror. This larger instrument will have sufficient sensitivity to also provide data on the quantitative concentration of atmospheric trace gases. (*** One possibility for the UV/visible spectrometer is to use the complete fibre-fed plug-in PC card spectrometers from Ocean Optics. However, it appears that their sensitivity may be too low. ***) Auroral all-sky camera: Lockheed already has such an instrument in the existing AGOs and at South Pole. The instrument uses 1 to 2 minute integrations on a bare CCD (a Ford 1024x1024 pixel chip, running at -50C), with a filter wheel for auroral lines, airglow, and for broadband observations (allowing it to see lots of stars, and hence determine the cloud cover). The instrument currently draws 300 W, but could be made in a low-power version. US$45K is an approximate indication of the cost. Gary Swenson and Steve Mendy are two useful contacts (Jack Doolittle has contact information). It was noted that an auroral all-sky camera is going in with an AGO at Dome C this summer (1995/96). Another way of looking at aurorae is to use satellite imagery. Dan Lubin has been looking into this (Al Harper has more information). It is very difficult to use satellite data to determine cloud cover over Antarctica, since it is hard to tell the difference between cloud and the ice when it is dark. DIMM: Gary Hovey circulated a document describing the conceptual design of the ANU DIMM instrument, with details of the various alternatives that he has considered for solving technical problems. For more information on the ANU DIMM, please refer to Gary's document. Only a few of the items are discussed here. Gary is proposing that the DIMM be aligned manually with an eyepiece on stars when first deployed. The software should be clever enough to allow the instrument to cope with subsequent alignment changes of up to a degree. Experience at the Pole appears to show that mountings can be made stable for over 12 months at the arc minute level. The guidance camera is expected to have a field of 15 minutes of arc. The optical configuration of the DIMM is still being planned. One interesting possibility is to use a microlens array. Storey made the point that the sensitivity of the DIMM increases towards the UV, both because the telescope's resolution increases, and the seeing gets worse. It would therefore make sense to use a blue filter in the DIMM, and to use a CCD with good blue response (*** perhaps by Lumogen-coating an existing CCD - Peter Conroy at Stromlo has expertise with this ***). The main cost in the mounting for the DIMM will be the encoders. After considering several alternatives, Gary has settled on inductosyns. These are electrically and mechanically robust, work well in the cold, consume about 1 W for each axis, and can give a resolution of 0.15 arcseconds for a cost of around AUD$15K (US$11K). They can give position and rate information, thereby eliminating the need for a separate rate-encoder for the motors. AST/RO uses inductosyns, and it was suggested that Gary contact Tony Stark for advice (*** he has since visited Tony in Boston ***). It was mentioned that if optical encoders are used, it is possible to send the encoder outputs back inside the AASTO using fibre optics, thereby allowing the electronics to work at room temperature. (*** One problem with optical encoders is that if the disks get covered in a layer of ice, they stop working - this has happened at Mauna Kea. ***) It became obvious that the DIMM mounting would be a useful sub-system for several other instruments, hence the concept of a Generic Mounting was born, and Gary was suggested as the logical contact person for this project. The idea is to engineer a platform that can be used for any of the experiments that require pointing (either multiple experiments per mount, or multiple mounts). There was discussion on the need to put the DIMM on a tower, both to get above any blowing snow and to sample the seeing at the height at which a ground-based observatory could be built. A 10 metre tower was considered to be the minimum desirable height. The tower needs to be light, stable, and able to be transported in an LC-130. Several instruments may need to share the tower with the DIMM. The DIMM design from Stromlo was based around a fairly slow readout ST-4 CCD camera. Bally, Loewenstein, and Peterson all urged the use of a TV frame-rate CCD system to capture more information. It would be possible to record the video output on a camcorder in the AASTO, running on lithium batteries. Multiple camcorders could be provided for around US$500 a unit. Ashley suggested that the DIMM could periodically drive through focus while recording the video signal, to get all the available information, thereby possibly allowing the height of the turbulence to be determined. Doolittle has information on a suitable CCD camera made by Pulnix, which he uses for the all-sky auroral camera. One has to be careful with cameras that use interline sampling, since information will be lost unless you oversample. To measure the low-level contribution to the seeing, there were two possibilities discussed: - Use microthermal sensors to measure the turbulence from ground level, through the height of the DIMM (and higher using a light-weight extension to the tower). - Construct a light source at height for the DIMM to measure. A tethered balloon could be used to support the light source (or a reflector for a ground-based light). These issues can be considered by the aasto.microt and aasto.skyhook groups. Near-IR: Michael Ashley gave a brief description of the near-ir spectrometer being planned by UNSW. The instrument would be similar in goal to the IRPS experiment currently at South Pole. A single element detector would be used, with the detector and filter being cooled by a Stirling cycle cooler. If only one filter is to be used, it would probably be a Kdark filter (i.e., 2.27 to 2.45 microns, designed to transmit in the ``cosmological window'' region of the K-band). Multiple filters are difficult to accommodate due to the very limited cooling capacity (a few hundred milliwatts) of the Stirling cycle coolers, which therefore requires a mechanical system for moving filters into place, ensuring that they are in good thermal contact with the cooler, and then waiting possibly for some hours before the filter is cold. The instrument would have a wide-field (perhaps 4 degrees), a small aperture (5 mm), and the ability to sample the sky at various zenith angles. No astronomical sources, apart from the Sun, Moon, and a few bright stars, would be visible with the instrument. (*** Stirling cycle coolers are improving in performance and mean time between failure (MTBF). Figures of 5000 hours MTBF have been quoted. One problem with Stirling cycle coolers is that they may not like working at low ambient temperatures (one company says that its coolers will not start at temperatures below -30C - although once started they will continue working down to lower temperatures. ***) Mid-IR: John Storey described the planned mid-IR spectrometer to be contributed by UNSW. It would be almost identical to the near-IR spectrometer except the detector would be sensitive to mid-IR radiation. The following two paragraphs closely follow John's article to be published in PASA. The proposed wavelength range is from 7 to 22 microns. The instrument will use a mercury cadmium telluride detector, cooled to 77K by a Stirling engine, looking out at the sky in a 1 arcminute field of view through a selection of ambient-temperature filters. It will be able to detect emission from ice crystals to an emissivity level of a fraction of a percent, and by measuring the sky brightness as a function of wavelength will be able to accurately determine the atmospheric transmission. A black body of accurately known temperature will serve as a reference source. The proposed filters would be a CVF covering 6 to 11 microns, the standard IR astronomy ``silicate filter set'' and further fixed filters at 17 and 22 microns. At 10.5 microns the clear sky radiance is very low (emissivities less than a few percent) for a typical antarctic water level content. Ice crystals have maximum emissivity near 12.5 microns with about 15% of this at 10.5 microns. Thus, observations at these wavelengths can determine the radiance due to ice crystals (which may contribute 1/f noise to astronomical observations). The sky radiance at 10.5 and 12.5 microns is only weakly dependent on precipitable water vapour (PWV) while a channel at 22 microns has a very strong dependence. Knowledge of the PWV then allows the transmission throughout the 20 to 30 micron window to be obtained from model atmosphere calculations. It was noted that many of the instruments can make measurements of the PWV. For example, the UV/visible spectrometer can measure the equivalent width of unsaturated water lines. The comment was made that although it is theoretically possible to extrapolate water-vapour measurements from one wavelength region into another one, in practice the atmospheric models, and complicating factors such as pressure broadening, are insufficiently well known to permit this to be done with any confidence. Jeff Peterson commented that it may be possible to use pyroelectric detectors for the mid-IR spectrometer, which would obviate the need to provide a cooler. He has been getting noise figures of 10K per root Hz at 350 microns, and would expect this to be a factor of 1000 better at 10 microns. See the section on the sub-mm instrument for more information. Far-infrared Fourier Transform Spectrometer (FTS): No one at the meeting had much expertise on this topic. It was suggested that Mark Dragovan be asked for his advice. A commercial FTS covering the range 100 microns to 1 mm could be bought, but would likely be very expensive and of greater spectral resolution than we would require. The optical bench would almost certainly have to within the AASTO itself, leading to some concern of water vapour contamination of the path. Jack Doolittle commented that this should not be a problem, as the AASTO is very dry. If the FTS looked out through one of the AASTO ports, care should be taken to ensure that there was no water-vapour contamination from the AASTO exhaust stack. With the current AASTO design, it is not easy to achieve this. Gary Hovey suggested that by rotating the AASTO by 180 degrees (so that the door is facing upwind) then the ports are upwind of the exhaust. Sub-mm bolometric tipper: Jeff Peterson already has been working on a prototype low-power sub-mm bolometric tipper, using a pyroelectric detector. The detector costs about US$400, has an area of 4 sq mm, a time constant of 1 second, a noise equivant power (NEP) of 10^-10 W/root Hz. The detector is made from a ceramic material, with contacts deposited on it which are sensitive to radiation. The detector is placed at the focus of a Winston Cone in order to increase its effective area. Two preliminary measurements on the closing day at South Pole this year showed sky temperatures of 150K and 200K at 350 microns, with a 10K sensitivity in one second. The noise goes as 1 over the freqency squared for a constant bandwith. So the shorter the wavelength, the less the noise. Jeff's original idea was to mount the detector horizontally, looking at a metal plate at 45 degrees rotating at 10 Hz, with two calibrating sources coming into the beam when below the horizon. He found that the microphonics from the rotator were too great, and so has reverted to using a lock-in amplifier and a higher speed chopper plate (alternately looking at the zenith and the rotating 45 degree plate). There was some discussion on sub-mm phase stability, which is of critical important if an interferometer is to be successful. One idea is to use an FTS with two inputs, separated by a few metres. Some people who know about sub-mm phase stability are Jean Cerrebin at the Caltech Sub-mm Observatory (CSO), Daryl Emerson (site manager at KPNO), Bob Martin at the University of Arizona, and Simon Radford (at NRAO). An experiment could be conducted at South Pole by looking at the signals from geostationary satellites. With sufficiently strong signals you could use omnidirectional antennae. It is best to use the highest possible satellite frequencies, in order to increase the sensitivity to small path-length changes. Microthermal measurements: Microthermal measurements can be used to extrapolate the DIMM results to both higher and lower altitudes. The microthermal sensors used by Jean Vernin at South Pole consist of very fine tungsten filaments: they have the unfortunate property of icing up after a few hours. This problem was overcome last year by covering the sensors when not in use, and by warming them with a heat source before use. Neither solution is probably practical for an AASTO. Alternative sensors may be possible, although the requirements of low thermal mass and fast time-constant (about 50 Hz) will necessarily make the sensors very small, and hence liable to accumulating ice crystals. John Storey is investigating solid-state sensors that are built at DSTO in Adelaide for use as thermal imagers. (*** After the meeting, Mike Dopita suggested that electrostatic attraction may be the cause of the ice accumulation, and if so, we may be able to create an electric field which would deflect the crystals. ***) The sensors could be supported on the DIMM tower, with a light-weight entension going up perhaps another 10 metres. An alternative idea from John Bally is to tether a small helium balloon and attach the sensors to one of the tethers. The balloon could even contain a small light source or mirror which could be observed by the DIMM, and used to obtain an indication of the ground-based seeing contribution. Scintillometer: Bally gave a brief description of the operation of a scintillometer. This instrument, developed for the US SDI program, typically has a 15-20 cm aperture with mask and a photon counting detector giving 10 ns time resolution (an intensified CCD was mentioned, but this couldn't possibly have this time resolution...). Jay Tilly at Philips Labs is a useful contact. A PhD thesis is available on the topic. The scintilometer effectively gives Cn^2 as a function of altitude, with 500 metre altitude resolution. It also tells you the size of the isoplanatic patch. A low power version may be possible. Acoustic sounder: These can be purchased for between AUD$30K and $60K (US$40K to $80K). Ian Bourne at the Australian Defence Force Academy (ADFA, in Canberra) has some experience with acoustic sounders. Bill Nef, who wrote a PhD thesis on acoustic sounder measurements in Antarctica, would be an ideal person to approach for advice. Acoustic sounders measure wind shear as a function of altitude, and can tell you the height and depth of the inversion layer. Their results are not as closely related to astronomical seeing as are microthermal measurements. Acoustic sounders probably need about 500 W of power to run, which could be accommodated within the AASTO power budget by having a 1:200 duty cycle (assuming a 50% loss in storage batteries). It would also be possible to operate a full-power sounder during the put-in and servicing visits for the AASTO. Ceileometer: A ceileometer employs a laser to measure the height of the cloud layer. It was suggested that the other experiments (e.g., DIMM, UV/vis spectrometer, auroral sky camera) are all capable of determining whether there is cloud about, so that a ceileometer is not necessary. Duty cycle of the AASTO: The point was made that power could be saved by not running instruments until after sunset, and if clouds were present. One would have to be careful that the sunlight/cloud detector didn't malfunction. Alternative power sources for the AASTO: Batteries can be used to store energy from the AASTO's 50W supply for later use, but the amount of energy that can be redistributed this way is a tiny fraction of the AASTO's yearly power output (Jack Doolittle calculated that 35,000 lb of batteries would be needed to provide 50W for a year). Solar power can be used when the sun is up, which is not very useful from an astronomical point of view. Wind power could be an important contributor. The steady winds at some of the AGO sites, combined with modern high-efficiency wind-generators, make it practical. However, a redesign of the AASTO's very successful power module is a major project that is almost certainly outside our brief. We should therefore plan to stay within the 50W budget (8W of which are used by the AASTO data acquisition system). Power supply issues: (*** While not discussed at the meeting, it may be a good idea to standardise the power supplies used for the various instruments. Issues such as fusing, battery storage for intermittent high-current usage, optimum battery charging strategies, efficient generation of a range of DC voltages, and so on, need to be addressed by almost every instrument group. To this end, a sub-project (``aasto.power'') has been formed to examine the issues and design a ``generic power supply.'' ***) Communications: There was much discussion of the possibility of increasing the data rate out of the AASTO from the 2 kbytes per day limit of each ARGOS channel, and in particular, the possibility of achieving two-way communication. One possibility is to use the ATS 3 satellite, which gives 1200 baud communication using a VHF/UHF channel. Another possibility would be the planned low-orbit satellites such as Project Iridium from Motorola. TEDRIS should be possible by 1998. Legislation prohibits amateur radio bands from being used for this purpose. It was generally agreed that instrument-designers should consider the possibility that two-way communication may be available by the time the AASTO is deployed, and in any case, such communication would be very desirable for the testing phase at South Pole. Generic mounting: There was agreement that many of the instruments would require a pointable, cold-engineered, low-power, mounting. Gary Hovey has been designing such a mounting for the DIMM instrument, and he agreed to act as a point of contact for a special interest group on the generic mounting. It is possible that the DIMM telescope itself could be used as a light-feed for other instruments, or other small telescopes could be piggy-backed on the DIMM mounting, or several mountings could be made for completely independent instruments. Al Harper mentioned that the Marshall Space Flight Center has an interest in robotic telescopes, and that we should contact them. Jeff Peterson raised the possibility that he may be able to obtain funding to assist with development of the generic mounting. Lockheed star-tracker: Lockheed has developed for NASA a star-tracker instrument with a 20 to 30 degree field-of-view. This device can recognise star fields with no knowledge of where it is pointing, and will then calculate its position to an accuracy of 5 arcseconds. Jack estimated that one of these units could be delivered for a cost of around US$200K. Heat pipes: Jack Doolittle has experience with designing heat pipes for spacecraft, with lengths from 5 cm up to 2 metres. He comments that the heat pipes with switching elements that are designed to regulate the flow of heat are in general not as reliable or as efficient as heat pipes with no regulation. A good source of a constant low temperature is the ice about 1 to 1.5 metres below the surface, where there is little yearly variation in temperature. A heat pipe could be made from copper pipe, with insulation to stop it being affected by the air temperature. The AASTO itself can be used as a source of heat, although this is difficult in practice. Jack Doolittle originally thought of providing a hot plate to which experimenters could bolt heat-pipes. However, the difficulty in guaranteeing thermal regulation of the AASTO under variable heat loads from experiments led Jack to abandon this idea. Tapping directly into the AASTO's freon is out of the question due to the danger of leaks causing loss of the freon. John Storey commented that if it was necessary to generate heat electrically, then it would be best to use a Peltier effect device (as a heat pump), rather than to use a resistor. Transparent domes: Jack Doolittle and Bob Loewenstein have experience with designing optically transparent domes to cover experiments. Michael Ashley commented that someone at South Pole had mentioned that it took them two years to get their dome to the state that it wouldn't condense on the inside: apparently dry N2 is not dry enough for use at -65C. (*** At the SPIE conference 2552 in July 1995 at San Diego, D. C. Harris from the Naval Air Warface Center spoke on ``Frontiers in infrared window and dome materials''. ***) Rocket sonde: The original suggestion for this came from John Bally and Frank Bartko. The idea is to loft sensors (meterological, microthermal?) up to 3 km into the atmosphere at regular intervals during winter. Suitable sondes are made by AIR Inc, Boulder CO. They are 1-inch in diameter and cost around US$300 each. A US$25 GPS transponder can give wind profiles to 0.5m/s accuracy. John Bally is to follow up on the possibilities of sondes. UNSW Antarctic Test Facility: It was mentioned that UNSW has been funded to set up an ``Antarctic Test Facility'' consisting of a refrigerator capable of -86C, and an AASTO Data Acquisition Unit. This facility will be situated in Sydney, and will be available to any AASTO investigator who wishes to use it. Deployment of the AASTO: CARA will be including the AASTO as part of the ATP project, and requesting its deployment to South Pole as part of the normal SIP process. Next meeting: It was suggested that sometime around August 22 to 25, 1995, or the week after, at Yerkes, would be a good time for a preliminary design review. With another opportunity in March 1996, and interface testing to commence in June 1996. ------------------------------------------------------------------------------ History: Mar 94 - AASTOWG established at the Yerkes Antarctic Experimenters Workshop. 09 May 94 - Letter send to John Lynch from John Storey (UNSW) and Jeremy Mould (ANU), putting forward the AASTO idea, and suggesting ways of arriving at a Letter of Intent whereby NSF expresses it committment to the project. Lynch forwarded the letter to csullivan, croberts, dpeakcock, echiang, sstephen, wslater, bsnavely,hvanhorn, all in the NSF, and a few other CARA people. 20 May 94 - Budgetary Estimate for AASTO made available by Jack Doolittle. 23 May 94 - First meeting of the AASTOWG, in Boulder, Colorado . 31 May 94 - UNSW submitted application for funding one-half of the AASTO. The application was made to the UNSW Discretionary Funding Scheme. 02 Jun 94 - John Lynch writes a supportive letter for the UNSW AASTO grant application, but can not guarantee logistical support for the program. Jun 94 - VXE-6 is tasked with determining if LC-130s can support an AASTO at Dome A. 16 Jun 94 - JACARA set up with MOU signed between UNSW and ANU. 21 Jun 94 - A meeting at NSF is told that LC-130s can not take off with the necessary cargo wieght required for Dome A. Even some of the planned AGO sites are not possible. 12 Aug 94 - UNSW AASTO grant application is successful. Sep 94 - ANU submits matching fund application. Jan 95 - ANU funding application is successful. Jan 95 - ANU begins design work on the DIMM. 21 Mar 95 - Lockheed supplies the first version of the Strawman Statement of Work. 01 Apr 95 - Second AASTOWG meeting, at Mt Stromlo in Canberra. 08 May 95 - Revised Strawman Statement of Work received from Lockheed. 10 May 95 - Lockheed receives Request for Quote for the AASTO. 24 Jun 95 - UNSW receives final quotation from Lockheed for the AASTO. ------------------------------------------------------------------------------ AASTO timeline: 10 Aug 95 - Place the order for the AASTO. Aug 95 - AASTO sub-project groups established. Aug 95 - Preliminary Design Review for the instruments. At Yerkes. 01 Dec 95 - Lockheed finishes AASTO, power module, and fuel system, and delivers them to Port Hueneme, CA, for ocean transport. Feb 96 - AASTO arrives in McMurdo. 01 May 96 - Lockheed delivers a Data Acquisition System to UNSW. 01 Oct 96 - Lockheed completes Power System and deliver to Port Hueneme for air transport. - Lockheed completes Meteorological Instruments for the AASTO and delivers them to Port Hueneme for ocean transport. - Prototype AASTO instruments (JACARA/CARA) are transported to McMurdo. Feb 97 - Power System and Meteorological Instruments arrive in McMurdo. - All AASTO components and instruments air shipped to the Pole. - Lockheed/JACARA/CARA participate in AASTO integration at Pole winter 97 - AASTO operates at Pole. Jan 98 - Last chance to make changes to instruments. - AASTO flown to Dome site. Jan 99 - AASTO flown to alternative site. Jan 2000 - Large telescope built on plateau :-) All AASTO investigators are now rich and famous :-) ------------------------------------------------------------------------------