Volume 33, Number 1
The mythological hero from the Volsunga Saga, Siegfried, passes through a ring of magic fire to win his bride. This scene is laden with symbolism, and I am going to concentrate on a single aspect of it: it is a hero's quest. Life is filled with hurdles to overcome, and on many occasions we all travel through the "magic fire" and emerge on the other side, stronger than we were before and better prepared. We all become heroes simply by living our lives to the fullest. The PhD qualifying exam, the thesis defense, and entering the job market are all events that we'd rather avoid, but when accomplished they make us untouchable; one can say, "look what I've done!"
The task of self-improvement never stops. The Buddha reminds us of this when he says, "onward, onward, ever onward to enlightenment." We here at the DAA have an excellent opportunity to further our knowledge and research skills, but at what cost? There has been much talk about producing graduates at a faster rate, and I wonder if the bar for PhD theses is not set too high? From the few chats I've had with visiting researchers who sit on PhD defense committees, I have received this opinion. It would be extremely unfair to try to force graduate students to do five years' worth of work in only four.
By concentrating on creating excellent researchers, our graduates have had a high rate of success of continuing on in their chosen field. But then we miss out on other aspects of higher education. I've said it before and now I put it in writing: there is no culture of excellence in education within our community, either department-wide or university-wide. A few of us get together every two weeks to hash out details of this or that, and progress can be made by those who are interested, but we are all deprived when the sum total of the Department's brain power is not set to work on any problem that the Department has to deal with. There are plenty of real, present-day problems that are looming over us, but more on that later.
It is easy for us to throw up our hands and say, "the university and/or government does not give us enough funding to teach well", but this statement is just passing the buck. If it is true (and at the UofT it undoubtedly is) then is it not also our job to take this message to the university, rather than just live on the table scraps that tumble off of table of the wealthiest university in the country?
So, by being here and doing what we, as a Department, do, we all become heroes and can proudly assemble our CVs and move forward. However, we as a group are incomplete, and eventually it will show: are we attracting the best money? the best students? the best professors? how is this situation changing over time? are we addressing these concerns properly? Suppose we submit these questions to a dialectical analysis: are we reaching an extreme? what antithesis will we be forced to face? are we going to like the result?
Hegelian dialectics suggests that any situation will react with its
opposite to synthesize a new situation. Mao Zedong thought that
dialectics can be manipulated: if you wish to achieve a certain
result, then you lay the foundation by encouraging something related
but different. When addressing the problems we perceive, a question
we must ask ourselves is, "are we going to be proactive, or reactive?"
MOST will be launched at the end of this year. It is a Canadian space astronomy project to perform seismology of Sun-like and oscillating stars from space, as well as to study micro-variability in Wolf-Rayet winds and other targets. It will be a very small, but capable micro-satellite. The PI of the mission, Jaymie Matthews, calls it the "Humble Space Telescope". This note is about its history and the current status MOST.
The author of this note and Kieran Carroll of Dynacon Enterprises Limited (and of UofT Institute for Aerospace Studies) were the successful applicants to the Canadian Space Agency (CSA) in 1997 to build the first Canadian micro-satellite. It remains the only micro-satellite in the CSA program. There have been plans to prepare a series of such satellites, but unfortunately a total silence on that prevails. One may hope that the unique experience learned while building MOST will not all be lost. We note that this is the first fully Canadian astronomical satellite, designed and built in this country.
The basic design of MOST and of its orbit was established in 1997. The satellite will stay on a Sun-synchronous, dusk-dawn, almost-polar orbit. Such an orbit is quite high above Earthís surface, with the typical altitude of some 850 km. From that height, the Earth limb is low and a wide angle opens up for continuous observations, called the Continuous Viewing Zone (CVZ) of the satellite, of some 54 degrees across. The plan is to observe one object in the CVZ, continuously for typically a month (observations up to 7 weeks may be possible), with the sampling rate of 10-30 seconds. Because there will be no Earth eclipses (like for the HST, unless an object is in its very small CVZ), an object could be monitored without any interruptions, providing unprecedented photometric precision in the definition of the oscillation spectrum at a level of a few ppm (parts per million or micro-magnitudes). The primary goal of the mission is to obtain oscillation spectra of a number of solar-type stars for modeling and comparison with stellar interior models.
|Caption: A wide angle opens up from the large height of the orbit, much wider than for the HST. The CVZ of MOST will have the opening cone of about 54 degrees. The satellite will observe the ecliptic sky with limits on the declination range of about -18 to +36 degrees.|
|caption: The solar oscillation spectrum obtained by the SOHO satellite. Similar spectra are expected from MOST for solar-type stars, particularly for subdwarfs as a means of providing a new constraint of the age of these oldest stars. Note the discrete frequencies of oscillations and the background caused by the solar granulation variability.|
MOST looks like a large, heavy suitcase: a 15-cm Maksutov optical telescope is mounted in a micro- satellite bus of about 50 kg in mass and with dimensions of about 60 x 60 x 24 cm. The satellite will be launched, together with a cluster of other micro-satellites, by a former SS-19 rocket (aka an ICBM "Stiletto") on December 17, 2002 from Plsetsk (this cosmodrome has sent more satellites than all other sites combined). The highly-manoeuvrable third stage, Breeze, will establish the final orbit. The Canadian Space Agency has been the first among several clients to initiate the launch so we will have the choice of the optimum orbit. As to how the initially tumbling satellite will stabilize and acquire its first object is a bit too much to write about - I will be happy to talk to you personally about it. Here, I can only say that it will involve almost-real-time work of bright graduate students.
|Caption: The satellite is shown here from its dark side (pun not intended). The large disk in the centre is a somewhat uninteresting but prominent mount-connector to the third stage rocket. The open lid is over a periscope mirror which feeds the 15cm telescope. The CCD radiator is the elongated dark feature at the lower left. The other, bright side of the satellite is all covered by solar panels. Some of them are also on the dark side, for the case of a loss of orientation when all electric power may be needed to restore stability.|
In orbit, the satellite will be stabilized by a set of miniature reaction wheels which will point the telescope to an accuracy of about 10 arcsec or better. This must be considered a considerable achievement because typical micro-satellites of comparable size can only be stabilized to within 2 - 3 degrees. The lucky circumstance of a meeting of Dr. Kieran Carroll (who developed the miniature reaction wheels at Dynacon & UTIAS) and of the author was actually the main reason why the mission is going to happen. We were also able to convince CSA that stars are the best objects to try small-payload stabilisation techniques (while doing some science on the side).
In our original design, we suggested the orbit (at that time this would be the secondary payload of the Canadian Radarsat-2 which is now delayed) and the main instrument design which envisages one side constantly illuminated by the Sun's light, with the other side in the darkness, exposing the 15cm telescope and its CCD radiator to the darkness and coolness of space. The dusk-dawn orbit would assure continuous viewing of the anti-solar skies permitting long, uninterrupted observations. The simple short-wave telemetry via two or three stations (Toronto, Vancouver, now augmented by a station in Vienna, Austria) and the whole internal electronic and computer design closely follows the well tested designs of AMSAT. Several of the bus subsystems have been flown on past AMSAT micro-satellites.
While the telescope can produce direct images over a part of the science CCD, the image of the program object will be positioned on a special array of micro-lenses. Each micro-lens, a few 100 microns across, will capture an image of the telescope pupil on a CCD. This image will be spread out over many (about 1000) pixels and will not move with the residual wobbles of the satellite, virtually eliminating photometric noise due to pixel-to-pixel sensitivity variations on the detector. Adjacent microlenses will produce comparable images of background sky fields, to correct for scattered Earth light and zodiacal light. The addition of the Fabry lenses is the major departure from (and addition by the UBC team) to the original 1997 design, but it should substantially improve photometric accuracy of the mission.
|Caption: There are two CCDs on board of MOST, each consisting of two areas, the active area and the storage area. This frame transfer design will permit exposures as short as 1 to 10 seconds. While there is no upper limit, the exposures will not be longer than a couple of minutes. The attitude control CCD is identical to the one shown, except that it does not have the micro-lenses covering part of the active area. While accuracy at the level of a few parts-per-million is expected for stars observed in the integrated mode (under microlenses), the in-focus photometry of field stars is expected to give results only some order of magnitude worse.|
|Caption: The two CDís have their active areas within the MOST field of view of about 1/2 degree. The Attitude Control System (ACS) CCD does not have micro-lenses, but otherwise is identical to the Science CCD. The storage and telemetry capacity will be such that parts of the Science CCD (about 1/3) could be sent down to one of the three stations during morning and evening passes. However, if only the two Canadian stations are used, then only integrated signals from the areas defined by the micro-lenses will be sent as numbers (not as images).|
The current design is expected to reach photometric precision of better than a few micro-mag in stars as faint as V = 6 in about ten days of observation. While simple time-series observations will profit from the high precision, the main point will be the perfect continuity and regularity of observations, permitting derivation of very clean oscillation spectra. The only limitation will be the very small size of the telescope and thus the quantum noise. Obviously, if we could afford a bigger telescope, the range in classes of objects would be considerably broadened. A few other missions, with larger telescopes are planned, the French COROT (30 cm, funded), the Danish MONS (40cm, planned) and the newest and the largest (95cm) addition, the NASAís KEPLER (to be launched in 2006).Our little satellite will have only one advantage: tt will be the first by at least a year or perhaps even more.
The targets currently selected for the MOST mission are solar-type and metal-poor (subdwarf) stars, rapidly oscillating Ap (roAp) stars and WR stars. The high precision of the observations should also permit us to look for signatures of reflection effects caused by planets on close orbits around a few solar-type stars. We have enough targets for the first and the second year (each 15 objects), although all this is very preliminary, as we are not sure about the acquisition efficiency. The orbit should stay synchronised with the Sun (i.e., will keep precessing at the solar rate) for some 4-5 years, so we may have many more objects to observe. There are plans to open the mission to a wider community, including amateurs.
My personal history and that of MOST are somewhat intertwined. When the first Sputnik started orbiting the Earth in 1957 and I was a young astronomy amateur in a high school, I had a rather obvious idea: "What if we could send my little telescope on the orbit and observe continuously?" I never expected that this would ever happen, especially after quite a few turns in my life. Anyway, forwarding to the 1990s: when the Ontario Centre of Excellence, the Institute for Space and Terrestrial Science, disbanded its astrophysics group in 1996, I was without proper employment and took a job at the CFHT. Then, in 1998, to everybodyís surprise, a word of acceptance of the MOST proposal came in. This was not good timing for me: the CFH Corporation did not agree on continuing involvement in the MOST. Fortunately, Jaymie Matthews accepted the leadership and is now beautifully handing all the PI duties. I have remained on the science team. Thus, Jaymie is the Principal Investigator of the MOST mission and Rainer Kuschnig is the Instrument Scientist (UBC) where the instrument is developed. The spacecraft is built at the Space Flight Laboratory of the University of Toronto's Institute for Aerospace Studies (UTIAS) with strong involvement of several industrial partners (see below).
The Science Team consists of Jaymie, myself, and five other astronomers: David Guenther (St. Mary's, Halifax), Tony Moffat (UMontreal), Dimitar Sasselov (CfA, Harvard), Gordon Walker (UBC), Werner Weiss (Vienna). The team had its meeting recently, on Dec. 7 and 8, 2001, in Boston. We discussed various operational aspects of the mission, but - most importantly - decided on the list of objects for the first year of the mission.
|Caption: The Science Team of the MOST satellite photographed during the December 2001 meeting. Standing, from left: Moffat, Weiss, Walker, Guenther, Sasselov, Kuschnig; seated: Matthews, Rucinski.|
Now about the industrial aspect of the undertaking. The satellite, whose total costs is about CAD$10M or US$7M), is funded primarily by the Canadian Space Agency, with additional contributions from the Province of Ontario and from University of British Columbia. Dynacon Enterprises Limited is the Prime Contractor for the mission, and is providing overall project management and systems engineering, as well as developing the satellite's Attitude Control Subsystem and its Power Subsystem. The optical telescope is being developed by UBC, with assistance from the Ontario Centre for Research in Earth and Space Technology (CRESTech). The MOST bus and ground stations are being developed by Dynacon and the Space Flight Laboratory of the University of Toronto's Institute for Aerospace Studies, in collaboration with AMSAT Canada. Because of the requirements on the imaging stability, the MOST attitude control system (ACS) utilises a highly accurate three-axis inertially-fixed stabilisation, far better than can be achieved using the gravity-gradient boom stabilisation approach typical of many past micro-satellites. Dynacon will provide the MOST Altitude Control System, based on its High Performance Attitude Control products, including the MicroWheel miniaturized reaction wheel actuator, and the MicroNode attitude control processor.
If you would like to read more about MOST, see the Web pages at:
I have received an interesting statistics on "impact factors" of publications. The message was distributed in Princeton and I received it from Bohdan Paczynski, but may have been written by Scott Tremaine. There is an interesting aspect to it (at the end) which pleased Polish astronomers publishing Acta Astronomica. - Slavek
------------------------------------------------------------------------ Date: Tue, 8 Jan 2002 12:13:04 -0500 (EST) From: email@example.com From tremaine@pollux.Princeton.EDU Sun Jan 6 11:56:18 2002 From: Scott Tremaine
To: all@astro.Princeton.EDU Subject: journals Those of you considering what journal to publish in might want to look at http://in-cites.com/research/2001/sept_17_2001-1.html which lists "impact factors" (citations in a two year period divided by papers published in the same period) for astronomy and astrophysics journals. The ranking is 1 Ann. Rev. Astron. Astrophys. (14.00) 2 Ann Rev. Earth Planet. (5.53) 3 Mon. Not. Royal Astr. Soc. (4.69) 4 Astroparticle Physics (3.61) 5 Astronomical J. (3.60) 6 Astrophys. J.-Suppl (3.48) 7 Astron. Astrophys. Rev. (3.46) 8 Acta Astronomica (3.18) 9 Pub. Astro. Soc. Pacific (2.90) 10 Astrophysical J. (2.82) Note in particular that - Astronomy & Astrophysics is not in the top ten. - Acta Astronomica beats Ap J. --------------------------------------------------------------------------
Fall Lecture Series, by Michael Allen
The DDO Fall Lecture Series was very successful again. It ran on Thursday nights between Nov 1 and Nov 29, 2001, for a total of five lectures. Twenty five enthusiastic people came out to learn about spiral galaxies. The lectures were organized as follows:
The lecture series was very enjoyable to give. Each night I gave a formal lecture for about an hour, after which we all relaxed in the DDO library over drinks and goodies and chatted about topics that interested the group. At the end of the series, the participants were so enthused that we all went out to dinner for a 6th and final meeting. I still get e-mail from some of these people with their questions or comments. What I particularly liked was that there were no tests or assignments, that the group was intelligent and energetic, and that I could concentrate on speaking about the most modern and exciting material.
The speaker for the 2002 Fall Lecture Series must be chosen NOW, and I encourage anyone who is interested to speak with myself, Peter Martin or Bill Clarke about what arrangements are needed. Past Lecture Series were given by Ernie Seaquist, Bob Garrison and Simon Lilly, all of whom have good advice to share.
Thanks especially to Lillian Lanca for providing all the refreshments and some entertaining observations, and to Toni Young for attending the lectures and giving me feedback on their delivery.
Traffic on info@astro, by Michael Allen
Some of you know that I have gathered together all of the e-mail aliases formerly used for sending inquiries to the DAA and DDO, and grouped them into a single alias, "info@astro". The info@astro alias is on the DAA and DDO homepages, and is printed on the DAA and DDO brochures. This address is generating messages at a rate of just over one per day.
Most of the messages I can handle myself, either because they are tour inquiries or because they are scientific questions that I know how to answer; a few years as the GASA sunangles person has proven to be quite valuable. Some questions I cannot answer and have forwarded them to those who can; my thanks to Bill Clarke, Ray Carlberg, Archie Ridder, Don Fernie, John Percy, and Christine Clement.
An interesting question came towards the end of January. I was told that in 2002 Passover falls on the Thursday before Good Friday. Therefore, the sequence of the celebrations this year repeats what historically happened: Jesus' Last Supper occurred on a Thursday, and was a Passover meal. The question I was asked was how often this Thursday-Friday sequence occurs. Passover falls near the date of the spring full Moon, and Easter falls on the following Sunday. Naively, one might guess that the Thursday-Friday sequence occurs on average about once every 6 or 7 years. However, the Passover celebration occurs on the 15th day of Nisan on the Jewish calendar, whose timing is dated from the date of the New Year, Rosh Hashanah. The Rosh Hashanah date is not allowed to fall on certain days of the week, because then the timing of some of the later festivals would fall on Sabbath days. Hence, dates of Passover tend to cluster around a few different days with respect to Easter.
Note (added Feb 27, 2002): the above calculation is incorrect. Please see the next issue of the Doings for the explanation.
Taking all of the above into consideration, I was finally forced to write a computer program to predict and compare all of these dates, and discovered that the Passover-Good-Friday sequence occurs 23 times in the 20th century and 22 times in the 21st century. It will occur next in 2003, 2006, 2009, and then not until 2020.
Another question came from a fellow who gave a very accurate description of a halo, and probably was the 22-degree halo one sees due to ice crystals in the air. Fortunately, for atmospheric phenomena there are two excellent books in the library: "Light and Color in the Outdoors", by Minneart, and "Color and Light in Nature", by Lynch and Livingston.
An alarming question I get a lot concerns the fictional "Planet X". The newsgroups are buzzing on this topic and misinformation abounds. A frightening result can come from an internet search; there is a lot of misinformation out there. The renewed interest in Planet X is a result of the search for Kuiper Belt objects, and near-Earth asteroid searches, both of which have turned up results.
Finally, I get questions about Sun and Moon angles. I use the NRC's sun angles website to answer these questions.
Answering these questions is fun. A single question can be
answered quite quickly, but when the questions add up then my time is
rapidly consumed. If there is anyone who enjoys answering scientific
queries and who would not mind fielding one, say, once every month,
then please let me know.
This section of the Doings is being discontinued, and will not appear after this issue. Simply put, preprints are no longer distributed on paper, and it is not the job of these editors to chase down electronic publication lists. To find publications by members of the DAA, DDO and CITA, the following lists are suggested: