Return-path: X-Andrew-Authenticated-as: 7997;andrew.cmu.edu;Ted Anderson Received: from beak.andrew.cmu.edu via trymail for +dist+/afs/andrew.cmu.edu/usr1/ota/space/space.dl@andrew.cmu.edu (->+dist+/afs/andrew.cmu.edu/usr1/ota/space/space.dl) (->ota+space.digests) ID ; Sat, 7 Oct 89 02:01:18 -0400 (EDT) Message-ID: Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Sat, 7 Oct 89 02:00:25 -0400 (EDT) Subject: SPACE Digest V10 #117 SPACE Digest Volume 10 : Issue 117 Today's Topics: Electronic Journal of the ASA, Vol. I, No. III ---------------------------------------------------------------------- Date: 3 Oct 89 19:40:23 GMT From: eedsp!chara!don@gatech.edu (Donald J. Barry) Subject: Electronic Journal of the ASA, Vol. I, No. III THE ELECTRONIC JOURNAL OF THE ASTRONOMICAL SOCIETY OF THE ATLANTIC Volume 1, Number 3 - October 1989 ########################### TABLE OF CONTENTS ########################### * ASA Membership Information - Don Barry * The Rocky Soviet Road to Mars - Larry Klaes * Alar Toomre: Galactic Spirals, Bridges, and Tails - Interview by Sethanne Howard, Edmund Dombrowski, and Don Barry * A Witch Satellite - Mike Burkhead ########################### ASA MEMBERSHIP INFORMATION The Electronic Journal of the Astronomical Society of the Atlantic is published monthly by the Astronomical Society of the Atlantic, Inc. The ASA is a non-profit organization dedicated to the advancement of amateur and professional astronomy and space exploration, and to the social and educational needs of its members. Membership application is open to all with an interest in astronomy and space exploration. Members receive the ASA Journal (hardcopy sent through U.S. Mail), the Astronomical League's REFLECTOR magazine, and may additionally purchase discount subscriptions to ASTRONOMY, DEEP SKY, and TELESCOPE MAKING magazines. For information on membership, contact Alan Fleming, ASA Treasurer, at 2515 N.E. Expressway, Apt. N-2, Atlanta, Georgia 30345, U.S.A., or call the Society recording at (404) 264-0451. ASA Officers and Council - President - Don Barry Vice President - Bill Bagnuolo Secretary - Scott Mize Treasurer - Alan Fleming Board of Advisors - Bill Hartkopf, David Dundee, Anita Kern EJASA Editor - Larry Klaes Observatory Search Committee - John Stauter Georgia Star Party Chairman - open Advertising Committee - Paul Pirillo, Willie Skelton Travel Committee - Chris Castellaw Sales Committee - Jim Bitsko Society Librarians - Julian Crusselle, Toni Douglas Telephone the Society Info Line at (404) 264-0451 for the latest ASA News and Events. ARTICLE SUBMISSIONS - Please send your on-line articles on astronomy and space exploration to Larry Klaes, EJASA Editor, at the following net addresses: klaes@wrksys.dec.com, or ...!decwrl!wrksys.dec.com!klaes, or klaes%wrksys.dec@decwrl.dec.com, or klaes@wrksys.enet.dec.com If you cannot send your articles to Larry, please submit them to Don Barry, ASA President, at the following net addresses: don%chara@gatech.edu, or chara!don@gatech.edu You may also use the above net addresses for EJASA backissue requests and ASA membership information. DISCLAIMER - Submissions are welcome for consideration. Articles submitted, unless otherwise stated, become the property of the Astronomical Society of the Atlantic, and although they will not be used for profit, are subject to editing, abridgment, and other changes. This Journal is Copyright (c) 1989 by the Astronomical Society of the Atlantic. THE ROCKY SOVIET ROAD TO MARS Copyright (c) 1989 by Larry Klaes The planet Mars has long been considered the first planet beyond Earth upon which humans will land and explore, possibly within the first decades of the Twenty-First Century. Already the United States and Soviet Union have sent a series of unmanned probes to the Red Planet, serving as "scouts" for eventual manned missions long in the planning stages. While the United States can boast of having had successful Mars missions, the Soviet Union has been less fortunate: The recent demise of their two PHOBOS spacecraft stand as a testament to the Soviet's rocky road to the Red Planet. It is important to look back on the Soviet's history of unmanned Mars missions to see what has gone wrong, what they have achieved, and what can be learned to create better exploration projects. Such studies will allow future Soviet and U.S. probes to gain more information and to pave the way for successful manned journeys in the future. The first attempts to explore Mars by spacecraft began in 1960 from the Soviet Union, just three years after the nation had placed the first artificial satellite, SPUTNIK 1, into Earth orbit. On October 10 and 14, two probes were launched from the Tyuratam Space Center towards an Earth parking orbit before their planned journey to Mars. The first probe, designated MARS 1960A by the West, had a failure in the third stage turbopumps of its A-2-e (MOLNIYA) rocket launcher and did not obtain the desired orbit. The second probe, MARS 1960B, suffered a similar fate. Though no details have ever been released on these probes by the Soviets, they may have weighed 850 kilograms (1,870 pounds) and were intended to flyby the target planet in May of 1961. There was also the rumor that Soviet Premier Nikita Kruschev, who was attending a meeting of the United Nations General Assembly in New York at the time of the launches, had brought a model of the vehicles with him to show off Soviet technological prowess at the Assembly. When LUNA 2 became the first spacecraft to reach Earth's Moon in 1959, Kruschev had personally delivered a model of the lunar probe to U.S. President Dwight Eisenhower during a summit meeting; but when the Mars launches failed, Kruschev's model never appeared in public. A third Mars probe mission in 1960 was believed for years to have been tied in to reports of a major rocket disaster, which the Soviets did not admit to officially, until a press release by Aleksandr Bolotin in the Soviet weekly magazine OGONYOK in April of 1989. The article stated that, contrary to information gathered earlier by Soviet space expert James Oberg, a rocket which exploded on the launch pad at Tyuratam on October 24, 1960 was not carrying a Mars probe, but was an attempt to launch an R-16 InterContinental Ballistic Missile (ICBM), better known in the West as the SS-7 SADDLER, which was designed and built by the Yangel Bureau. The R-16 explosion killed dozens, perhaps hundreds, of engineers and technicians at the launch site, including the Soviet official in charge of the rocket project, Field Marshall Mitrofan Nedelin, Commander in Chief of the Strategic Rocket Forces. There may have been a third unsuccessful Soviet attempt to send an unmanned probe to Mars by the end of 1960 after the first two failures, but this has yet to be confirmed. Despite all that had gone wrong with their Mars probes in 1960, the Soviets were ready to send unmanned spacecraft to the Red Planet again when the next launch window arrived in 1962 (A launch window is the period of time when Earth and Mars are so aligned in their solar orbits that a relatively large payload can be sent using the least amount of rocket energy, saving both time and fuel). The first of the three probes launched that year, MARS 1962A, did obtain Earth parking orbit on October 24, but half an hour after the orbital insertion, the rocket stage attached to the probe - which would have sent the vehicle on to Mars - unexpectedly exploded. The resulting debris sailed on, and was soon picked up by several Ballistic Missile Early Warning System (BMEWS) stations in the Northern Hemisphere. There were a few anxious moments that the debris might have been an incoming Soviet nuclear missile attack on the U.S. (the launch had occurred during the height of the Cuban Missile Crisis), but the defense computers quickly determined that this was not the case, and World War Three was abated. A second Mars probe was launched from Tyuratam on November 1, and it became the first such Soviet vehicle to actually leave Earth orbit. The Soviets officially announced the probe's existence and intentions to the rest of the world, and designated it MARS 1. The Soviets also released pictures and descriptions of the craft: MARS 1 was a 893.5 kilogram (1,970 pound) spacecraft consisting of a cylindrical "bus" 3.3 meters (10.89 feet) long which housed both scientific instruments and course correction engines. The bus was flanked on either side by solar panels which supplied power to the instruments, and a high-gain "umbrella" antenna located on the front of the bus. This same basic design has been used for Soviet Mars and Venus probes from that time to the present, albeit with some upgrades and modifications. The main objectives of MARS 1 were to study the interplanetary medium on its way and to flyby Mars at a distance of less than 11,000 kilometers (6,600 miles) and to photograph the planet's surface. MARS 1 was to have also sent back measurements on Mars' magnetic and radiation fields, cosmic radiation, micrometeoroid impacts, and even indications of organic compounds on the planet using a "spectroreflexometer" device. The mission proceeded well through early 1963. On March 16, MARS 1 broke the distance record for interplanetary communication recently set by the first successful U.S. Venus probe, MARINER 2 - 86.7 million kilometers (52.02 million miles). Sadly, this was to have been one of the probe's last accomplishments. Several days later, Soviet controllers noted that MARS 1 was having troubles with its orientation system, and when the craft could not keep its communications antenna locked on Earth, all contact was lost. It is believed that MARS 1 did fly past its target planet on June 19 at a distance of 193,000 kilometers (115,800 miles), but returned no data. The Soviets blamed an errant meteoroid which struck the probe and broke the ground link. Some Western experts blamed the loss on a faulty attitude control and/or communications system which had reached its technological design limits. In any event, it was a dark sign of things to come for the Soviet Mars program. Three days after MARS 1 had been launched in 1962, another Mars probe, unofficially designated MARS 1962B, was put into Earth orbit; but like 1962A, it too broke up before leaving orbit. The spacecraft and rocket debris eventually burned up upon re-entering Earth's atmosphere in the ensuing months, the last pieces disintegrating on January 19, 1963. The Soviets did not acknowledge its existence. The next good window for launches to Mars took place in late 1964, and this time the Soviets were not alone in exploring Mars with spacecraft. The United States sent two unmanned probes to Mars on flyby photographic missions: The first one, MARINER 3, ceased functioning soon after its launch on November 5 when the protective shroud around the craft failed to eject. Unable to open its solar panels to receive energy, the probe's batteries were soon exhausted and MARINER 3 drifted off into solar orbit dead. NASA scientists quickly corrected the problem with its sister probe, MARINER 4, and it was successfully sent to Mars on November 28. Two days later, the Soviets launched a Mars probe with the generic name of ZOND 2 (Zond is the Soviet word for probe). Its intentions were similar to the MARINERs, and there was speculation in the West that ZOND 2 also carried a capsule lander to study the Martian surface. The evidence for a lander was based on its estimated weight of 1,145 kilograms (2,519 pounds), 251.5 kilograms (553.3 pounds) heavier than MARS 1, which had no lander, plus the fact that ZOND 2 seemed to have been launched to minimize its arrival speed at Mars, thus reducing the problems of atmospheric entry for a lander. One device verified aboard the spacecraft was a set of six experimental plasma (ion) engines designed to assist in attitude control. In spite of this technical innovation, it was noted soon after launch that ZOND 2's initial power supply was fifty percent below the expected level. This may have contributed to the loss of communications with the craft in April of 1965. ZOND 2 was later estimated to have flown past Mars at a distance of roughly 1,488 kilometers (930 miles) on August 6, 1965, less than one month after MARINER 4 flew by Mars and obtained the first close-up photographs of the Martian surface (twenty-two in all). There was some concern for a while that ZOND 2 had actually impacted on the planet, as it was not decontaminated of Earth micro-organisms before its launch. Western scientists feared that the bacteria might "interfere" with any Martian organisms present, or could at least confuse future missions searching for life into thinking that Earth organisms possibly deposited by ZOND 2 were native to Mars. In any event, no impact has ever been confirmed. Though the Mars launch window had passed by 1965, the Soviets sent up another ZOND probe on July 18 of that year. ZOND 3 was designed to be an engineering test of spacecraft systems for future Mars and Venus missions, no doubt due in part to the concern over previous mission failures. ZOND 3 flew past the far side of Earth's Moon on July 20, where it took the first photographs of the lunar farside since LUNA 3 in 1959. Soviet controllers then sent the probe on a trajectory out to the orbit of Mars. As ZOND 3 sailed outward, it transmitted back its lunar photos at various distances in a test of the communications system. ZOND 3 continued to transmit data on interplanetary space until March of 1966, when it was 153.5 million kilometers (337.7 million miles) from Earth. Though ZOND 3 did cross the orbit of Mars, the craft was nowhere near the planet at the time. The 1967 launch window to Mars was passed up by both the Soviets and U.S. as they concentrated on sending spacecraft to explore Venus during that period, as well as preparing for more ambitious unmanned missions to the Red Planet. While the U.S. was building its next series of more sophisticated flyby probes - MARINER 6 and 7, which completed successful photographic surveys in 1969 - the Soviets were testing their next generation of Mars explorers in the atmosphere and in Earth orbit. Throughout the late 1960s, there were reports of the Soviets testing a lander capsule aeroshell and parachute system for a future series of unmanned Mars landers. These flight models were dropped at high altitudes from aircraft to test their aerodynamic capabilities, much as the Jet Propulsion Laboratory (JPL) in the U.S. was doing with its VOYAGER mock-ups (later to be known as VIKING) around the same time. In 1969, two (and possibly three) spacecraft of the new Soviet Mars exploration series were launched. Weighing far more than any earlier Mars craft (approximately 3,500 kilograms/7,700 pounds), they were sent aloft on the powerful D-1-e (PROTON) rocket booster. These probes most likely consisted of a flyby bus which would drop a lander on the Martian surface as the bus headed on into solar orbit. Unfortunately these latest spacecraft were plagued by old technical problems: MARS 1969A, launched March 27, was destroyed on its way into an Earth parking orbit when the PROTON booster exploded in mid-flight. MARS 1969B, launched on April 14, may have been destroyed in the same manner as its sister probe, as it too never achieved Earth orbit. A third member of this set, MARS 1969C, reportedly never even left the launch pad at Tyuratam, for reasons which are still unknown. All in all, it was not a glorious beginning to such an ambitious new program. Nineteen seventy-one was a very busy year for exploring Mars with spacecraft, in part because the launch window was so favorable. The first U.S. and Soviet attempts failed miserably: MARINER 8, launched on May 9, ended up in the Atlantic Ocean instead of around Mars when an autopilot fault in the ATLAS-CENTAUR rocket sent the craft off course. The Soviets had equally bad luck the next day: What might have been officially designated a MARS probe instead became COSMOS 419 when the vehicle failed to leave its parking orbit around Earth. Initial success was achieved nine days later, when MARS 2 escaped Earth's gravitational well. It was followed on May 28 by MARS 3. The U.S. rounded out the Mars launches two days after MARS 3 with MARINER 9, which also found its way on to the fourth planet from the Sun. MARS 2 and 3 were more advanced than previous Soviet Mars probes: Weighing 4,650 kilograms (10,250 pounds) each, the probes carried two 450-kilogram (990-pound) landers designed to photograph and examine the Martian surface. The lander design was based on that of the 1966 LUNA 9 and 13 Moon probes: A sphere kept upright by four metal "petals" which opened around the lander's base after landing. The crafts' main buses contained rocket thrusters designed to brake the probes for insertion into orbit around Mars, where they would serve both as scientific stations and as orbital relays for the landers' signals back to Earth. Even the project's design team was of a new generation, averaging less than thirty years in age. The team was supervised by veteran mission specialists. Although it was launched from Earth later, MARINER 9 arrived at the Red Planet earlier than its Soviet counterparts, and became the first spacecraft to orbit Mars on November 14, 1971. MARS 2 came on the scene November 27, followed by MARS 3 on December 2. While this was going on, far below the vessels a global dust storm had enveloped Mars, with no signs of abating. For MARINER 9 this meant few visible surface features to photograph while it waited for the dust storm to clear, but for the Soviet probes the consequences were far greater. Due to design limitations, the Soviet probes had to release their landers before injecting themselves into Mars orbit; they could not wait for the dust storm to end like MARINER 9 did. MARS 2 ejected its lander 4.5 hours before going into orbit. The plan was for the lander to enter the thin Martian atmosphere at supersonic speeds protected from heat friction with the air by an aeroshield. Once past this critical phase of the descent, the shield would be ejected after a parachute was released to slow the craft even further. Just before touchdown, the lander would fire retrorockets to cushion the landing impact to a survivable velocity. On the surface, the metal "petals" would open outward to balance the lander, which would immediately start to relay a panoramic view of its surroundings to the orbiting bus for transmission to Earth. The lander would then carry out various measurements of the immediate environment until its battery power was exhausted. Sadly, the MARS 2 lander's mission was to be cut drastically short. Whether because of the dust storm or mechanical problems, the lander apparently crashed onto the surface at 45 degrees south/58 degrees east in the planet's southern hemisphere. Though no data was returned from the lander, it does hold the distinction of being the first human-made vehicle to reach the surface of Mars. The MARS 2 bus subsequently went into an orbit ranging in altitude from 1,380 to 25,000 kilometers (828 to 15,000 miles), circling the planet once every eighteen hours. MARS 3 initially had better luck than its counterpart. Arriving in orbit on December 2, the lander headed towards the surface, where it came down three minutes later in Mars' southern hemisphere at 45 degrees south/158 degrees west between the regions Electris and Phaethontis. Ninety seconds later, the craft's timer mechanism ordered a panoramic scan of the lander's surroundings; but just twenty seconds into the scan, the signals ceased. A partial picture was returned, but it "did not reveal any noticeable difference in the contrast of details", according to a Soviet report. Once again the Soviets blamed the dust storm which was engulfing Mars as the reason for the demise of the lander - it may have been saturated with fine sand, or knocked over by strong winds - but some Western analysts suggest that the MARS 3 orbiter had some telemetry problems, not the lander. With the lander missions now permanently defunct, Soviet controllers concentrated on the scientific studies made by the orbiters. Photographing the planet's surface proved frustrating, as the dust storm continued to blot out most Martian features. After several weeks the imaging part of the mission was given secondary status, while MARS 2 and 3 concentrated on measuring the Martian atmosphere and surface. The orbiters discovered atomic hydrogen and oxygen in the upper atmosphere, and that the average temperature on the surface ranged from 13 degrees Celsius (55.4 degrees Fahrenheit) at noon to -110 degrees Celsius (-230 degrees Fahrenheit) at night. Portions of the planet's night side were found to be twenty to twenty-five degrees warmer than some of their immediate surroundings. Atmospheric pressure on the ground was recorded at 5.5 to 6 millibars (by comparison, air pressure on Earth averages 1,013 millibars at sea level), and water vapor was scarce. The orbiters were subsequently turned off in March of 1972, several months after the dust storm had settled down. It should be noted that MARS 2 and 3 were the first Soviet spacecraft to actually arrive at the Red Planet while still communicating with Earth. By 1973 the United States had announced plans to send two spacecraft to Mars which would not only study the planet from orbit in more detail than before, but also land two vehicles which would study the Martian surface and search for signs of micro-organisms. These probes were known as VIKING 1 and 2, and would be launched from Cape Canaveral in Florida in late 1975. Perhaps spurred on by this ambitious U.S. plan for exploring Mars, the Soviets launched their most complex mission to Mars in 1973, in an attempt to gain some prestige, after the U.S.'s impressive accomplishments at the Red Planet. Since 1973 did not possess the most favorable window to launch an orbiter-lander combination Mars probe (the PROTON rocket could not handle the weight load of such a vehicle in such a "steep" window), the exploration tasks were divided amongst four vessels: MARS 4 and 5 would orbit the planet, relaying not only scientific data but telemetry from the landers, which would be deposited on the Martian surface by MARS 6 and 7. The buses of the landers would sail on into solar orbit after delivering their loads. MARS 4 was launched first on July 21, followed by MARS 5 four days later. MARS 6 was sent aloft the following month, on August 5, with MARS 7 bringing up the rear three days later. Being the first of the series launched, MARS 4 also arrived at Mars first on February 10, 1974; but instead of going into orbit as planned, the probe's main braking engine failed to fire, and MARS 4 drifted past the planet at an altitude of 2,200 kilometers (1,320 miles) before heading off into an unscheduled orbit around the Sun. MARS 4 did relay a number of pictures of the Martian surface as it flew by the planet. MARS 5 reached the Red Planet just two days after its sister orbiter, successfully firing its breaking engines for orbital insertion, which ranged in altitude from 1,760 to 32,560 kilometers (1,056 to 19,536 miles), making one revolution around Mars in just over twenty- four hours. In addition to its original scientific duties, MARS 5 also had to serve as the communications relay for the MARS 6 lander, since MARS 4 was no longer available to do the job. Together with MARS 4, MARS 5 took sixty images of the Martian surface, comparable in quality to those taken by MARINER 9 two years earlier. In fact, MARS 5 gave the first serious evidence that most of Mars' surface was bright orange-red in color (the color filters on MARINER 9 had malfunctioned very early in its mission). The Soviet probe's findings were later corroborated by the VIKING orbiter images. MARS 5 also found an ozone layer thirty kilometers (eighteen miles) above the planet's surface. In addition, the probe revealed that the outermost layer of the atmosphere consisted of atomic hydrogen twenty thousand kilometers (twelve thousand miles) above the planet. MARS 5 was the only Soviet Mars probe which accomplished all of its planned tasks to date. The Soviets did not reveal when the craft's mission was terminated. MARS 7 was the first of the flyby/lander probes to arrive, the bus ejecting its lander towards the planet on March 9, 1974. Unfortunately, though the lander was intended to land at 50 degrees south/28 degrees west, it instead missed the entire planet by 1,300 kilometers (780 miles), apparently due to a major fault in either its solid-propellant motor or attitude control system. The second flyby/lander, MARS 6, was the last of the set to reach Mars, successfully deploying its lander on March 12. The lander performed as designed during its descent to the surface, relaying back to Earth the first direct atmospheric readings of Mars, which seemed to indicate a high concentration of argon. Two minutes and twenty-eight seconds into the descent - just twenty seconds away from touching down at 24 degrees south/25 degrees west - signals from the lander ceased. Why contact with the lander stopped is unknown, but it was certainly a disappointing end to the series. Even the argon reading made by MARS 6 was found to be erroneous two years later by the successful VIKING probes. A combination of discouragement and replanning - plus the great accomplishments of the VIKING probes from 1976 to 1982 - was no doubt part of the reason why the Soviets launched no more unmanned Mars missions after the MARS 4-7 series until almost the end of the next decade, when a new generation of probes and commitments to Mars exploration were made with the PHOBOS series. PHOBOS was different from all previous Soviet Mars missions, not only in the fact that it was the first such project announced by the Soviets to the world several years in advance of its launching, but also in its spacecraft design and goals: The 6,000 kilogram (13,200 pound) probes were aimed to explore the relatively tiny Martian moon Phobos (and possibly even its smaller natural satellite, Deimos) with a number of small landers, a first in space history. Studying the Martian moons would also be of great benefit to future human explorers, as the satellites' proximities to Mars and weak gravities serve as excellent "space stations" for crews preparing to land on Mars. Two PHOBOS spacecraft would be launched from Earth in the summer of 1988 and go into orbit around Mars early the following year. The orbiters would wait several months, studying Mars and its moons while they achieved the proper trajectory to flyby Phobos at the incredibly low altitude of fifty meters (165 feet). It would be at this point that the orbiters would drop off three landers (one from PHOBOS 1 and two from its sister craft), two of which would anchor themselves by means of a harpoon into the dusty surface of the small moon, while the other would use a metal bar to move across Phobos' surface by "hopping" until its batteries ran out of power. The landers would send images and information about the moon to their orbiters, which would relay the data to Earth. The United States would play a vital role in the communications aspect of the mission - just as the Jordell Bank radio telescope in Great Britain had done for the Soviets in their Mars missions two decades earlier - by using NASA's Deep Space Network (DSN) of radar to pick up PHOBOS' weak signals. The complexities of the mission and the international cooperation was meant to be a sign of things to come in the Soviet's new ambitions towards exploring the Red Planet. PHOBOS 1 left the launch pad at Tyuratam on July 7, 1988, aboard the PROTON rocket booster. PHOBOS 2 was sent to Mars on July 12. While the probes were in transit towards the Red Planet, studies of the Sun and the solar environment were being carried out. On August 31, PHOBOS 1 was being prepared for an international solar experiment. During one of the regular communication sessions with the probe, a message with one character accidentally omitted was sent to the craft. This seemingly minor incident quickly snowballed as PHOBOS 1 was subsequently given a computer command to shut off its attitude control system. The resulting error caused the probe to begin tumbling, aiming its solar panels away from the Sun. Power in the spacecraft dropped dramatically until it could no longer function, and communications ceased. Despite several days of intense efforts by the Soviets to re-establish contact, PHOBOS 1 was permanently silent. Mission officials became extremely cautious about ensuring the continued functioning of PHOBOS 2, as it was now the only PHOBOS spacecraft left to carry out the mission objectives. But even their pampering was not enough to keep PHOBOS 2 from developing troubles of its own: As the probe neared Mars, the main fifty watt transmitter malfunctioned, leaving only the five watt backup to keep the craft in touch with Earth. The main bus cameras and several scientific instruments also malfunctioned, though they were later corrected as PHOBOS 2 went into Mars orbit on January 29, 1989. For the next two months, the craft spent its time examining Mars and Phobos, while adjusting its altitude above the planet to match that of its target moon. Placement of the two landers on the surface of Phobos was set to occur around April 7. On March 27, almost two months to the day after PHOBOS 2 was placed in orbit around the Red Planet, controllers ordered the craft to orient itself to take photographs of Phobos. Since the probe's main antenna was not on a separate swivel platform from the orbiter, the entire craft had to be turned away from Earth while the picture set was being taken. It would then reorient itself to transmit the images to Earth. Instead, the technical problems which have haunted the Soviet Mars missions since their beginning caught up with PHOBOS 2: The orbiter turned away for the imaging, but did not turn back. For two hours after the mishap, Soviet controllers tried to raise the probe. They were rewarded for thirteen minutes when faint signals were received from the craft, but soon after the signals disappeared and PHOBOS 2 was not heard from again. It was surmised that, like its sister probe, PHOBOS 2 soon began to tumble without control from Earth, and lost all power when its solar panels moved away from direct sunlight. Two main theories arose as to the cause of PHOBOS 2's silence: Either a piece of debris - perhaps a meteor or even the probe's jettisoned propulsion module - had struck the spacecraft, disorienting it and pointing the antenna away from Earth, or the attitude control system - possibly a faulty gyroscope - had malfunctioned when the craft turned away from Earth to photograph its target moon, and could not aim the spacecraft back at its planet of origin. Project officials have since come to agree that the second theory, mechanical failure, was the culprit. The Soviets officially wrote off PHOBOS 2 on April 18, 1989. Ironically, the orbit of PHOBOS 2 might inadvertently cause the probe to become the first human-made vehicle to reach the surface of the Martian moon, though certainly not in a manner it was intended to. Before the PHOBOS probes were sent on their way, the Soviets had outlined an ambitious program of Mars missions, leading up to a manned landing by the year 2025. While the timetables will most likely be readjusted in light of the PHOBOS failures, it is hoped that the Soviets will continue with their plans, undaunted by the past. One new element in the plans for exploration could be the launching of PHOBOS 3 in 1992, the next favorable launch window to Mars. Formerly the ground test vehicle for its predecessors, PHOBOS 3 could be refurbished for a space mission and sent out to take over the scientific tasks so abruptly abandoned by PHOBOS 1 and 2. Other Soviet Mars vehicles include a combined orbiter/balloon/ lander mission in 1994, where a French-made balloon with an instrument package suspended underneath would float over the Martian surface through the planet's thin atmosphere, while smaller probes would either be soft-landed or penetrated into the reddish soil to take direct readings of surface conditions. An ambitious project planned for launch in 1996 would involve a Phobos probe that would actually land on the surface of the Martian moon and return samples of Phobos to Earth, while other spacecraft instruments would remain on Phobos for further observations. The next project calls for a robot lander to place an unmanned rover on the Martian surface, designed to explore the planet with a far greater range than the immobile VIKING landers could. If successful, this could lead up to a joint rover/sample return mission conducted by the Soviets and United States: The U.S. would provide a rover that would bring samples of Martian soil and rock to a Soviet lander, which would then launch the precious cargo back to Earth for direct examination (if the rover failed to function properly, the Soviet lander would still have the ability to scoop up some soil at its touchdown site for return to Earth). The Twenty-First Century might also see a manned Soviet mission to orbit Mars, with an eventual surface expedition as a prelude to colonization. These expeditions could be carried out as joint ventures with the U.S. and other nations, creating numerous scientific and political benefits in the process. The Soviets have had a difficult three decades in exploring Mars with spacecraft, but not without some important accomplishments. It is hoped that they will not be daunted by their setbacks, as it should be realized that humans are still pioneering the exploration of space, in spite of our numerous advances. The time, effort, and human lives spent in reaching other worlds should not be in vain because of technological and political obstacles. All nations have had their initial failures when exploring space, only to eventually succeed in one capacity or another. Our future descendants on Mars and throughout the Solar System will thank us for our efforts. Bibliography: Gatland, Kenneth, ROBOT EXPLORERS, The MacMillan Company, New York, 1972. ISBN 0-7137-0573-6. Hart, Douglas, THE ENCYCLOPEDIA OF SOVIET SPACECRAFT, Exeter Books, New York, 1987. ISBN 0-671-08932-3. Johnson, Nicholas L., THE SOVIET YEAR IN SPACE 1988, Teledyne Brown Engineering, Colorado Springs, Colorado, 1989. Miles, Frank, and Nicholas Booth, RACE TO MARS: THE MARS FLIGHT ATLAS, Harper and Row, Publishers, New York, 1988. ISBN 0-06-016005-5. Oberg, James E., UNCOVERING SOVIET DISASTERS: EXPLORING THE LIMITS OF GLASNOST, Random House, Inc., New York, 1988. ISBN 0-394-56095-7. Smith, Arthur, PLANETARY EXPLORATION: THIRTY YEARS OF UNMANNED SPACE PROBES, Patrick Stephens Limited, Wellingborough, Northamptonshire, England, 1988. ISBN 0-85059-915-6. Wilson, Andrew, SOLAR SYSTEM LOG, Jane's Publishing, Inc., New York, 1987. ISBN 0-7106-0444-0. ALAR TOOMRE: GALACTIC SPIRALS, BRIDGES, AND TAILS An interview by Sethanne Howard, Edmund Dombrowski, and Don Barry At the winter meeting of the American Astronomical Society (AAS) in Boston, we were fortunate enough to spend some time with the irrepressible Alar Toomre of the Massachusetts Institute of Technology (MIT), one of the world's leading theorists (and, as he might say, "computer experimentalist") whose work has led to many explanations for the formation of spiral structure in galaxies. The following records an interview we conducted with him on the final day of the conference. Sethanne: How did you get into this type of work? Alar Toomre: Well, I studied about 25 years ago as a young instructor in applied mathematics at MIT, had been brought up in aerodynamics, and thought I might do some geophysical things like ocean flows, or the core of the Earth. But as it happened, I heard a talk by Professor Woltjer, who until recently was director of ESO. He came to visit us for a month at MIT, and I remember him telling us how thin the gas layer is in the Galaxy. It is thinner than a phonograph record, and it bends on one side. So I was thinking of warps in this disk, and the hydrodynamics, and for some reason I got into instabilities in the horizontal, like spiral making and so on. But by the late Sixties, Chris Hunter and I were finishing our paper on the warping of the Galaxy, and for a while we thought this was a mode, that this would distort and stay warped forever like Lynden-Bell had suggested, but it turned out it couldn't be because if it had a smooth, blurry enough edge it wouldn't stay put, and would run away and not look nice. And of course we know the Galaxy is warped, so we wanted to know what could possibly cause it; and we had a brainstorm that must have occurred to about ten different people before us, and that was that clouds came by and did it. There was this big, big push, especially by me - Chris Hunter thought I was being much too silly, because I got hung up about which orbit it might have been and so forth - and after wasting about three or four months of my time fooling around with warping the Galaxy, I checked out what happens to the Galaxy horizontally. And that's when I discovered for myself what a wonderful spiral it would cause. You wouldn't notice the warp, but you would see the wonderful spiral. Also it happened that my brother had just gotten his PH.D. about five years after me, and he and I were saying that "brothers ought to do something together", and for a year or two we were thinking about the Earth's core, and that didn't go anywhere and didn't do anything distinguished; but then when I had this beautiful tidally made spiral, not M51, but at least in that direction, boy, he seized upon it! He loves his graphics, and said, "I've got all the computing time, and would love to get this set up at the Institute for Space Studies in New York." One thing led to another, and we started on what became this fairly famous paper on [galactic] bridges and tails. Sethanne: How did you make the movie? Toomre: My technique for making movies "is to have a brother." Other people have a sister or a father, but I have a brother. It was a nice collaborative effort, it was the only time we ever collaborated, and it led to the Astrophysical Journal article, talks at the American Astronomical Society, two or three movies, and the Scientific American article. Sethanne: And the Astrophysical Journal article has no equations. Toomre: Once we got into this business, we got a lot of encouragement [from] a lot of nice people, [Halton C.] Chip Arp included. He didn't believe much of it, but knew it was at least honorable competition. Also from Donald Lynden-Bell - I remember he said "drop everything else, concentrate on this," so, after a number of hints like this, we did concentrate on this, but even so it took about two years of hard work to do all the searching and polishing and improving and speculating and so on, and we decided to do several impressive things, and rather than trickle it out as the usual four or five papers, we decided if we could possibly do it, we would write it into one paper. And we did. It was the thickest paper in that year's Astrophysical Journal; it was 43 pages, and the nominal page limit was 20, but it wasn't hard getting it past [Helmut] Abt [editor of ApJ], because it was computer written and you could split it up, but what's the point - and he agreed. The other thing that we determined, because we were engineers by background and loved our drawings, was to make the final drawings superlative. I was especially determined, and I overlaid these computer things by blank paper, and with India ink and templates, drew one patch and another patch, then taped them together nicely, and I put the lettering in and put the orbits in, a real labor of love. Our living room table was busy for four months more or less, but we were determined to be super in this because we were going to sell them! Both of us then had mathematics department affiliations, I at MIT, he at NYU, and we decided that, goodness gracious, why bother showing to the readers that we know that F = ma and a few others, so we determined not to put a single equation into our paper. Don: I don't know that much about galactic structure, but I know that tidal disruption has been postulated as the origin of spiral structure. What is your feeling about where it comes from? Toomre: Well, most of it surely comes from the inside, from the "heart", you know, unless there are hidden, unseen companions; but look, bar-making is surely an internal problem: There's no way you can make that tidally, and bar-associated spirals are internal. Also the messes, the M101 like multiarm spiral arms, are almost all internal. Tides are very good at making two-arm things, but they're not good at making four-armed things. If you see a four-armed thing, you can be certain you're safe - they weren't made by tides. Don: I guess M33 is an example of that, with two big spiral arms and a few smaller ones? Toomre: Yeah, M33 is another nice example - unfortunately, most of those are rather ratty NGC's, [like] NGC 6941 - we don't generally remember them, but they are the majority of galaxies; but, on the cover of many astronomy textbooks, or at least on the frontispiece, and if not on the frontispiece then at least on the first diagram in the chapter called galaxies, lives M51. Now clearly, M51 reeks to high heaven of being interacting. It is sort of the world's foremost spiral galaxy with a companion, and makes you wonder whether a companion did it - and [it] almost certainly did. But now let me go on. On the cover of the Hubble Atlas of Galaxies, the famous Hubble Atlas by Sandage, a classic book, there is embossed into the cover a picture of M81. Most people don't tend to think of M81 as an interacting spiral, but think of what's nearby it - M82 is nearby it. Sethanne: I didn't have the guts to put that diagram up [in the display paper]. It's the same diagram as M51, and works out analytically the same. Toomre: So what I'm saying is that we must be at least very alert that we don't get fooled by the fact that the most beautiful spirals in the sky might be exceptions. They won't stay exceptions - if we lived long enough, another hundred million years, two hundred million years, they might not be so impressive. In a billion years they'd be dull again, but while the fun lasts, they're pretty nice. They made a splash. A wave-like splash; and actually, the so-called density wave theory, which hypothesized that they lasted essentially forever, that was strictly speaking wrong. I'm pretty sure (that) almost no galaxies keep their form forever and ever, or even through many revolutions; but still, while the fun lasts, it's largely a density wave, an evolving density wave, my feeling. Now C. C. Lin, he still believes that most of the good spiral structure is long-lived, not forever, but revolutions upon revolutions; but that's where the fun comes in - there'd be no fun when everything's obvious. Sethanne: I believe it was you who showed that the density wave theory had a problem in damping itself out. Toomre: It has a number of problems, but I certainly saw that as one of the early whoppers. Anything is complicated when there are many players, many, many gravitating players - never mind authors - and there are all sorts of tricky interactions. You can't do it by arm-waving, you simply have to sit down and pluck at it. Ed: Having been exposed to a lot of new techniques at this conference, which ones do you propose would work with these interacting methods? Toomre: Most things are not revolutionary, most things are evolutionary. Most things get better, sometimes by a big wallop, like this tree code idea in the n-body calculations is a real revolution, by factors of ten in efficiency. To do something a hundred times more efficient, you can do lots of things: Careful studies, careful searches, things you wouldn't have dreamt of doing. Whenever experimentation becomes more feasible with one hundred times less effort, like has been happening in this decade with computing and good software that goes with it, lots of things become possible. Observationally, of course, think of the CCD's: They make quantitative measurements at low light levels very very possible, whereas they were huff and puff and inaccurate at that before. Clearly, deep imaging of all sorts is terrific and needs to be done and needs to be done with clever filters and so forth, as it is being done by some people for IRAS [InfraRed Astronomical Satellite] objects and quasars. I expect a real growth in this industry, maybe from the Hubble Space Telescope, maybe from the ground, and I expect more cases to show up where quasars are actually imaged in their vicinity and there are distinctive interaction signatures: A tail or two, or a ring of two, where you have to salute finally, not just talk. So I expect things to get better in several ways, partly observational and partly computational, and once in a while, partly theoretical. Sethanne: Could you give us some personal background on your work before galaxies? Toomre: I'm an immigrant to this country from Europe - actually an Estonian who came to this country as a thirteen year-old kid, saw the Statue of Liberty and all that. We were refugees - dawdled around Germany after the War for five years, and then came to the States in '49. [I] went to Ohio briefly, but things got better, I went to Long Island, and then less than four years later was a freshman at MIT. In fact, it was like the Vietnamese boat kids of this era. After MIT, there were aerodynamics and physics. I enjoy airplanes to this day, and followed details in that crash recently [Pan American disaster in England] with interest. Engineers learn much more from disasters than they do from smooth operation. After that I went to England actually for aerodynamics research and a PH.D., partly because I was curious what postwar Europe was like, and after that I came back to MIT, only for two years, but in the math department. Oddball thing, they were hiring in applied mathematics, and aerodynamics kind of counts as applied mathematics; but astronomy has always been vaguely my hobby, but I had no idea that anyone would ever pay me to pursue my hobby, and so one thing led to another. Two years I was out of a job, briefly [was] in Princeton as a visitor, and then I was invited to come back [to MIT] as an assistant professor, which was very nice. Don: Do you have any advice for today's amateur astronomer? Toomre: Let me ask your amateurs to think for themselves one thing: I would have guessed that the day is coming, maybe has already come, where the amateurs, with their computers, can already begin to be amateur n-body calculators, not just observers, not theorists either, but amateur experimenters. There are several parts to astronomy: Observation is King, they are the biggest thing, but people often befuddle theory with experiments. Of course you can't experiment with galaxies, but you can experiment with imitations thereof, in fact computer imitations, and I've really been wondering when it is that the amateurs with their PCs don't just calculate where Venus will be and dull things of positions, but actually do some significant science. Sethanne: Astronomy magazine has recently published Arseth's code in BASIC to run on a PC, and it works great, makes lovely little pictures. Toomre: But of course the kinematics of interactions can be done without Arseth's code - you need some simple integrators, fairly accurate so they don't lose all accuracy in the first orbit or so, and you need some visualizing, at least some color graphics and an Epson printer that makes some good symbols, but I think amateurs can to a great extent delight themselves with the feeling that they are not too far behind the pros by doing and repeating essentially my own or others twenty-year old published things, because they are really in the amateur class now, and amateurs can imitate it for fun. Also ring galaxies are even more fun, you drop a galaxy right through another disk, drop it a little off center, and what a wonderful variety of shapes you can get. Sethanne, Ed, and Don: Thank you, Dr. Toomre, for a wonderful interview, and best wishes in your work. Toomre: Thank you. A WITCH SATELLITE by Mike Burkhead On Halloween nights, witches are often imagined by little children to fly in the night sky between Earth and the full Moon. One such evening, very briefly, I thought they really did. On Halloween, October 31, 1987, I arrived home after work and saw a clear Georgia twilight sky, with the Moon waxing gibbous. I thought this would be a good time to get out the telescope for lunar observing. I could even leave it set up for the children making their rounds trick or treating. As I focused my 60mm refractor on the Moon, the ocular filled with light. I adjusted the scope so that the southern region of the Moon was in one side of the eyepiece, and twilight in the other. Suddenly, the unexpected happened. I saw something black appear at the edge of the Moon's image! As it began to move across the lunar face, I wondered aloud what the heck was going on. Suspecting a bug crawling on the objective lens, I checked the front of the scope. The lens was clean and clear, with no insect to be found. I thought I was seeing things. Back in the ocular, the black spot was still there, moving across the Moon. My mind made associations: Halloween, Moon, Witch! It's a witch. I moved away from the scope and looked at the Moon with the naked eye. Nothing was in motion; the Moon was by itself. With the witch theory discarded, I decided to study the dark object more closely. By now I had to adjust the scope so the northern area of the Moon was in the field of view. The object was still traversing the Moon at a very steady rate, but it appeared to be twirling or tumbling. Eventually, it moved off the edge of the illuminated Moon and vanished. I looked up at the sky and saw no further traces of it. Was it a man-made satellite? It had to be; but unlike other satellites that I have watched crossing the heavens, the sky was too bright to see the satellite itself, or else it was in Earth shadow and had no light of its own. I take back all the times I've said I have no luck - I've never won anything, but the odds of being in the right place and looking at the right time to see the silhouette of an artificial satellite as it transited the moon must be "astronomical". Although my explanation seems long, the event only took ten to fifteen seconds to transpire. I suppose the satellite was of Soviet origin, since it travelled south to north in polar orbit, as many Soviet satellites do. All in all, it was truly a splendid sight to see, and probably a once-in-a-lifetime experience. The only thing I remain a little curious about is "witch" satellite it actually was. THE ELECTRONIC JOURNAL OF THE ASTRONOMICAL SOCIETY OF THE ATLANTIC October 1989 - Vol. 1, No. 3 Copyright (c) 1989 - ASA -- Donald J. Barry (404) 651-2932 | don%chara@gatech.edu Center for High Angular Resolution Astronomy | President, Astronomical Georgia State University, Atlanta, GA 30303 | Society of the Atlantic ------------------------------ End of SPACE Digest V10 #117 *******************