Saturday at the 1998 Astronomical League Convention


Alan BellSaturday started out with "Retrofitting Stanford's Boller & Chivens Mount - The Challengers" by Alan Bell. Mr. Bell discussed the techniques used to update an older mounting at Stanford's Observatory. They wanted to add motor drives and optical encoding to make the telescope more usable. Mr. Bell discussed the problems of interference between encoder cables and electrical power cables. He also described the techniques to properly mate the drive gear with the worm gear.

Deep Space-9 is a science fiction space station, but Deep Space 2 is the first in a new series of NASA "microprobes". These tiny explorers are only 6-inches across and two inches thick with a 6-inch whip antenna. DS-2 Project Manager Sarah H. Gavit explained the mission to us.

The DS-2 mission (also known as the Mars Microprobe Project) will be launched on a Delta rocket, hitchhiking on the Mars Lander. Upon reaching Mars, the Cruise Ring Module which carries the solar panels, will release the main Lander. It will then eject the two DS2 microprobes. The microprobes, each surrounded by a basketball-sized aeroshell will enter the Martian atmosphere. The aeroshell's shape is designed to work like a badmiton birde -- no matter how you hit it, it always orients itself the same way, eliminating the need for an active attitude control system. The aeroshell protects the probe as it enters the Martian atmosphere and begins to slow down through atmosphere braking. The probe will hit the surface at 400 miles per hour. This shatters the brittle aeroshell and the probe will embed itself one to six feet into the Martian surface.

After landing, the probe pushes a "penetrator" further down into the Martian ground under the probe. The penetrator, now deeper in the dirt of Mars, will then use a sideways-pointing drill to bore into the Martian soil and obtain a sample. The sample will be heated to check for water. The results will be sent back to the Mars Global Surveyor for transmission to Earth.

Sarah GavitWhile the mission sounds easy, there were many unknowns that had to be solved before the mission could fly. First the probe itself had to be tested. This required that the probe actually impact the soil. To perform this test, they first tried to drop the probe from airplanes. As a money saving action, they would send the probe up with skydivers. The problem was that the lander could fall anywhere in a half-mile radius, and they were hard to find amid the desert vegetation. While it was acceptable to lose test bodies, as they started to build the actual probe, they could not to afford to lose the more complex hardware.

They then switched to testing with a large gun that would fire the probe into the ground at various speeds. They would then dig out the probe to see how far in it sank. To test the basketball-sized aeroshell, they had to find a bigger gun which they eventually had to jury-rig themselves.

To test the entry characteristics of the aeroshell, they had to find a hypersonic wind tunnel. Many in the United States had been shut down by various cost saving measures. They finally found that the Russians had an operating hypersonic wind tunnel, and would do the testing job for only $40,000! This was another big savings and the Russian engineers were very professional and efficient.

The DS2 probes are scheduled for launch in January 1999. The primary mission will last two days. The total cost for the two microprobes, including all the engineers, testing, and scientist to analyze the data is 25 million dollars, less than a tenth what it cost to make the movie Titanic.

Darien StephensThe last talk of the morning was Darin Stephens on "Future Manned NASA Missions to the Moon and Mars". In 1991 President George Bush stood with the three Apollo 11 astronauts and promised that the United States would return to the Moon, this time to stay. Furthermore, we would also send a manned mission to Mars. A synthesis panel was convened and came up with a outline for accomplishing these goals. Lunar exploration would commence, and might be used as a training ground for the Mars mission. An observatory would be built to study the stars from the airless lunar surface.

The Mars mission would be divided into manned and unmanned segments. All launches would be performed with Saturn V or Energia-class rockets. There would be no near-Earth in-orbit operations, nor any near-Mars in-orbit operations before the landing. The first unmanned cargo segment would include a habitat, Mars ascent vehicle, and Earth return vehicle. This would occur in 2007. This would include an automated fuel manufacturing plant and a fueling system to fully load the ascent vehicle. The second segment would launch in 2009.

After the cargo launch, a high-energy orbit launch will occur carrying the manned mission to Mars in just 180 days. They will stay for 600 days and then return to Earth. While they are there, the second cargo mission will land bring additional supplies and equipment along with another ascent vehicle. Shortly after they leave Mars, another manned mission will leave Earth headed toward Mars. The first Mars crew will brief the second Mars crew while they are en route. This will lead to a continuing presence on the Martian surface.

The afternoon session began with the introduction to next year's ALCon, to be held in Spokane, Washington. Mickey Moreau tempted us with the facilities at Eastern Washington University in Cheney, Washington, about 20 minutes from downtown Spokane. On site accommodations will be available as well as a variety of hotels and motels in all price ranges. Camping is also available in the area.

For those who have visited the Northwest, we know you'll be delighted to be visiting us again. For those who have never been here, you've got a major treat in store for yourselves and your families. Spokane (we say, spocan) is the hub of the Inland Empire. Surrounded by forests, mountains, lakes, rivers and some of the most unique farmland in the world, there is visual beauty at every turn. From the Spokane River and its falls, located in downtown Spokane, to the gem of Lake Coeur d' Alene (that's coor d lane) in nearby Idaho, or into the gentle rolling hills of the Palouse (pa loose) farm country, this is a special part of the world.

The Spokane Astronomical Society is the proud host of ALCon 1999. Their society motto is, "Astronomy, for the Fun of It", and that is just what they intend for the 1999 convention. The S.A.S. is planning events, workshops and activities that will provide fun and knowledge for astronomers of all ages and skill levels. We hope to see you there! For further information visit their web site at http://www.spokaneastronomical.org/alcon99.html.

Dr. Richard SchmudeDr. Richard Schmude told us about "The Virginid Meteor Shower". The Virginid shower is a very low intensity shower, lasting over 100 days. If you were to actually look for Virginid meteors, you would see only seven in an entire night. Two primary observers of this minor shower, Robert Lunsford and George Zay, have reported a maximum Zenith Hourly Rate (ZHR) of 1.2 during the first ten days of April. Their observing program that ran from 1992 through 1996 has netted only 138 of these meteors.

Dr. Schmude then discussed a number of other aspects of meteors, meteorites and meteor showers. Most meteors are caused by tiny grains of dust striking the upper atmosphere at a very high speed and being vaporized. Larger grains produce brighter meteor trails in the night sky. Very large grains, really small rocks, create "fireballs" as they strike the upper atmosphere. Fireballs are meteors that are brighter than magnitude -4. Really large fireballs that are brighter than magnitude -8 may be big enough to survive their entry into our atmosphere and reach the ground. A meteor that does land on the Earth is called a meteorite.

In studying data from the various meteor organizations, Dr. Schmude found that there was no correlation between the number of observed fireballs and the number of actual meteorite falls. This indicates that while there may be meteor streams that have an abundance of larger grains, they do not necessarily have rocks in them large enough to reach the ground.

Most meteor streams come from the debris left by comets as they disperse gas and dust along their orbit. When the Earth encounters a comet orbit, the cometary debris slam into the Earth's atmosphere. Since they all came from the same source, they all have the same velocity and when they hit the atmosphere, parallax makes them appear to be coming from the same point on the sky, called the radiant.

Most meteors come from the comets which provide only tiny grains. The larger rocks that become meteorites seem to occur more randomly and do not inhabit meteor streams. This is born out by data that show for the latitude range of 40-degrees to 60-degrees north there is no correlation between the meteor rate and the meteorite fall frequency. There is also no correlation between the number of meteorite dropper fireballs and the meteor fall frequency.

The only positive correlation that Dr. Schmude was able to report was a possible correlation between the rate at which meteorites fall and apex of the Earth's orbital motion around the Sun. This is to be expected since the Earth's orbital motion sweeps up any meteoritic material ahead of it. This includes the larger meteors that would become meteorites.

Dr. Schmude encouraged amateurs to begin observing meteors in an organized way that would allow their observations to be used in scientific research. Meteor observing is also a relaxing and fun activity that allows the observer to enjoy the sky while making a contribution to science.

Dr. James KalerThe next speaker was Dr. James Kaler speaking on "Extreme Stars - At the Edge of Creation". Dr. Kaler started by describing the life of a typical star, our Sun. The Sun started out as a cloud of hydrogen gas. As it condensed, the temperature in the core of the Sun began to rise as gravity pulled in more and more material compressing the core. It finally gets hot enough to start fusing hydrogen into helium. The helium "exhaust" of the hydrogen burning accumulates in the core of the Sun. After some ten million years, enough helium has accumulated to create even higher temperatures in the core and it starts to burn forming carbon and oxygen.

The outer atmosphere of the now red giant Sun begins to drift away from it. Eventually only the core will be left. But in the process, the Sun will grow to almost the size of the Earth's orbit. The Sun in this stage is an extremely unstable Mira variable. These stars change their brightness irregularly over long periods. HST pictures of Mira variables show that they are not spherical but bizarrely shaped, probably changing over time.

The outer atmosphere usually ends up forming a dust disk around the star. Light and gas can still escape out through the polar areas forming a bipolar flow. These appear as jets flowing out from the star and striking the gas previously ejected forming many unusual shapes. As the star continues to die and nuclear fusion ends, it finally begins to shrink and compresses one final time to form a white dwarf star.

After this description of a normal star, Dr. Kaler went on to tell us about the extreme stars. Eta Carina ejected a solar mass worth of material in the mid-1840s that hid the light from the star. It faded from first magnitude to almost seventh. It is now starting to brighten again. This blue supergiant is the most likely star to turn supernova.

Betelgeuse is another huge star that will someday go supernova. Right now it is a huge, angry red star in the shoulder of Orion. Another red star is Herschel's Garnet star that is the size of the orbit of Saturn and is visually very red in color.

A supernova explosion blows off the outer atmosphere of the star and the resulting object might become a neutron star. Its magnetic field is unaffected, and the energy coming out through the magnetic poles can sweep across the sky. If the beam happens to point toward us sometimes as the star spins on its axis, it will appear to flash on a regular basis. This is what we see as a pulsar.

For more information on how various stars are different, visit Dr. Kaler's website at www.astro.uiuc.edu or e-mail him at kaler@astro.uiuc.edu.

Mary DombrowskiThe final speaker for the afternoon session was the National Young Astronomer Award winner for 1998, Mary Dombrowski of Glastonbury High School, Glastonbury, CT. who spoke on "Cataclysmic Stellar Variability with Eclipsing Binary Superposition". Ms. Dombrowski studied the variable IP Pegasi. This star is interesting since it is a cataclysmic variable in an eclipsing binary system.

We can learn much about stars in an eclipsing binary system. By observing the time between eclipses, we can determine the orbital period of the secondary and use that to determine the total mass of the two stars. From spectroscopic information, we can determine the two star types and hence their relative masses. We can then assign the exact masses of the stars and their approximate sizes.

IP Pegasi consists of a normal star, smaller and cooler than our Sun (spectral class K5), and a white dwarf star. The white dwarf is a massive compact star that pulls gas in a stream from the outer atmosphere of the normal star. This stream falls onto an accretion disc spinning around the massive white dwarf. At the point where the stream hits the disc, the kinetic energy of the falling gas is converted into heat and light, forming a "hot spot". This hot spot's brightness depends on how much gas is falling onto the accretion disc. In the IP Pegasi system, the flow from the normal star reaches a high every three months or so, causing IP Pegasi to go into outburst and brighten by two magnitudes.

Ms. Dombrowski's project had three goals. The first was to get real time data on the brightness of the IP Pegasi system through direct observation. The second goal was to show the worth of the contribution that amateur astronomers can make to astrophysical research programs. Finally, she wanted to participate in the ongoing investigation of the very interesting IP Pegasi system.

Ms. Dombrowski started her study by observing IP Pegasi every 10 minutes for five hours. She could only do this when IP Pegasi was in outbust, making it bright enough for her to make magnitude estimates through her Celestron-11 telescope. From this brief data run she was able to plot the light curve of the eclipse. As part of her project, if she saw that IP Pegasi had brightened (was in outburst), she would alert the American Association of Variable Star Observers (AAVSO) who would, in turn, alert NASA and the European Space Agency (ESA). During her observations, Ms. Dombrowski was able to observe IP Pegasi while it was in outburst on three different occasions.After plotting the light curve, Ms Dombrowski concluded that IP Pegasi has a period of 3.78 hours.

She also wanted to get a precise light curve of an eclipse in IP Pegasi by its unseen companion during a quiescence interval. To this end, she contacted Dr. Ron Zissell at Mt. Holyoake College, MA. Working together, they observed at Mt. Holyoake's observatory with a Photometrics CH250 CCD system. Taking a magnitude estimate every four minutes over a 68-minute interval, she was able observe an entire eclipse. The star varied from magnitude 14.7 to 16.9 at its faintest.

(Recent research has shown that the disc of IP Pegasi, which is smaller than the radius of our Sun, has a trailing spiral structure with two arms. Further analysis of the orbital period variation also shows a 4.7 year periodicity. This can be explained by a third body (late M dwarf) with a mass between 0.08 and 0.16 of the mass of the Sun. This periodicity cannot be explained by magnetic activity on the secondary star because the associated variation in brightness of the secondary star is not observed. For more information on the actual observations of spiral arms using Doppler tomography visit http://star-www.st-and.ac.uk/~ds10/spirals.html. There are some simulations of spiral arms in accretion discs at  http://www.cita.utoronto.ca/~armitage/.)

IP Pegasi will continue to be investigated at all wavelengths by NASA, ESA, professional and amateur astronomers. The results of these observations will allow astrophysicists to increase our understanding of the stars that make up the IP Pegasi system and the interaction between them.

The evening banquet provided an opportunity for awards and thanks. Mitch Lumen, on behalf of the convention co-chairs, thanked the entire Convention Committee for their hard work. The Great Lakes Region awarded Fr. Jim Fahey a lifetime achievement award. The Astronomical League also presented their awards.

The after Banquet speaker was former astronaut F. Storey Musgrave, who spoke about his part in the Hubble Space Telescope repair mission. The Hubble Space Telescope, the most expensive telescope ever built, had its optics ground by Perkin-Elmer who were already providing optics for military reconnaissance satellites. They performed the rough grinding with an optical tester. When they got to polishing and figuring, they got a new collimator.

This collimator did not appear to function properly, and so they inserted a few washers in it to correct the readings. This caused the unit to provide the wrong readings, and as they continued working on the mirror they introduced spherical aberration. When they checked it with the original tester, they saw the spherical aberration, but the pressure was on to get the mirror completed. The team concluded that the original tester was wrong because it was older. The team mentality allowed this incorrect decision to be reached, just as another team it did in the Challenger accident. An individual who was responsible would never have let it happen.

Once in orbit, there was nothing that could be done until the first repair mission. Astronomers and optical engineers designed the replacement Wide Field and Planetary Camera (WFPC 2) to include optical corrections so it would provide the originally-designed-for excellent images. They also replaced HST's High Speed Photometer (HSP) with a device called COSTAR (Corrective Optics Space Telescope Axial Replacement) system. This unit is a complex set of additional mirrors that would unfold in the optical paths of the other instruments, correcting their optical systems.

The HST repair mission was assigned the designation STS-61. The crew assigned to the mission were: Richard O. Covey, Commander; Kenneth D. Bowersox, Pilot; F. Story Musgrave, Payload Commander; Kathryn C. Thornton, Mission Specialist 1; Claude Nicollier, Mission Specialist 2; Jeffrey A. Hoffman, Mission Specialist 3; and Thomas D. Akers, Mission Specialist 5. As Mission Specialist 2, Swiss astronaut Claude Nicollier operated the remote manipulator arm during this mission.

With its very heavy workload, the STS-61 mission was one of the most sophisticated in the Shuttle's history. It lasted almost 11 days, and crew members made five EVA sorties, an all-time record. The flight plan allowed for two additional EVAs, but these turned out not be necessary. In order to bring off this mission without too much fatigue, the five extravehicular working sessions were shared between two alternating shifts of two astronauts. Astronauts Thomas D. Akers and Kathryn C. Thornton would work together on alternating EVAs. Jeffrey Hoffman would ride the arm to help position equipment and to assist Story Musgrave who floated free in the cargo bay.

Dr. Musgrave on RM arm with HST.As the Payload Commander, Dr. Musgrave was responsible for making the mission a success. This started with the pre-flight preparation. The replacement of the equipment on the HST had to be analyzed to see if the astronauts could actually do the replacement. In order to work in zero gravity with tools that rotate (screw drivers, wrenches, etc.), an astronaut had to be anchored in three places. These usually were both feet and one hand. This left the other hand to operate the tool. If the astronaut could not execute the maneuver, it had to be redesigned.

To see if it really would work, they set up a HST mock-up in the EVA water tank and the astronauts would "suit-up" and execute each space-walk maneuver. While in space, the astronaut would be weightless in the suit. But in the tank the astronaut would be supported by the suit. If he had to be upside down, all his weight would be pressing on his shoulders. This could be extremely painful.

Space is very cold, being about 3-degrees Kelvin. (-452-degree F.). While the sun is warm, it covers such a small area of the sky that anything exposed to space cools rapidly. The only large, warm object is the Earth, so the Shuttle is usually turned with the cargo bay toward the Earth, which averages 72-degrees F. This keeps the cargo bay warmer, but it can still get cold. Again, all the equipment had to be tested at the temperature it would be used to verify that it would work in space. Space suit gloves are insulated, but still handling very cold tools will draw the heat out of the astronaut's hands. In the pre-flight preparation, Dr. Musgrave suffered severe frostbite on his hands.

Another enemy they had to face was time. There was only so much time available to complete the repair mission, and they had to minimize the amount of time spent out in the cargo bay. Dr. Musgrave came up with a way of replacing the failing rate gyros that were far back in the HST equipment bay. Dr. Musgrave discovered that he could get in to replace the rate gyros from the bottom of the HST instead of the side. He had to prove to the management team that he could get in without scraping against any part of the HST. If he did, this would cause dust and metal flecks that could settle on the optics, destroying the usefulness of the HST. This saved an hour during the repair mission.

The repair mission itself went well. Launch occurred on December 2, 1993. The "flapping" solar panels were replaced, but the old panels would not retract, and had to be jettisoned before the new ones were completely tested. Fortunately, they worked well. (For more information on the actual EVA, visit the NASA website at: http://www.ksc.nasa.gov/shuttle/missions/sts-61/mission-sts-61.html)

Dr. Musgrave's talk was very interesting and the slides taken during the training and the mission were spectacular. With the end of his talk, ALCon 1998 came to an end.

 




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