henry@zoo.toronto.edu (Henry Spencer) (10/09/90)
[Okay, I guess we can take it that the Canadian Post Orifice has definitely eaten my copy of the Aug 13 issue of AvLeak, so there will be no summary of it. Stay tuned to see whether McGraw-Hill manages to foul up the renewal of my subscription yet again... they've only had my cheque for three months now...] Orbital Sciences reports its financial position improving, with revenues rising steadily and breakeven imminent. NASDA postpones launch of the BS-3A broadcast satellite at least three weeks due to a helium leak in ground-support equipment at Tanegashima. Soviets press for more cooperative programs, citing tight budgets at home. One project that they are studying themselves is a reusable manned spacecraft to replace the rather old Soyuz. First new science results from Hubble: WF/PC image of star cluster in the Large Magellanic Cloud shows considerably more detail than best Earth-based images (pictures included for proof), and the situation improves still further with computerized image enhancement. This cluster was a good target because it is bright; there is little hope for successful image enhancement of dim objects, and even the bright ones will need longer exposures than with correct optics. Magellan enters Venus orbit Aug 10, checkout underway. [This was before Magellan acted up.] Discussion of plans for Magellan after its 243-day [1 Venus year] primary mission ends. Objectives for the second and third "cycles" are fairly well-established: the second will fill the various gaps in the first's coverage [caused by, e.g., the Sun getting between Earth and Venus] and will start mapping of the south polar region (not covered at all by the first cycle), while the third will fill remaining gaps, improve south polar coverage, and study the detailed structure of Venus's gravitational field by transmitting a beacon signal to the Deep Space Network for precision tracking on some orbits. There are a number of ideas for later cycles: - Remapping interesting areas at a consistent side-look angle, to give similar features similar appearance; the initial mapping campaign varies the side-look angle continuously due to varying orbital altitude during each pass. - Remapping interesting areas while looking forward or aft along the ground track, to give better contrast on linear features that are perpendicular to the track. - Stereo imaging by mapping interesting areas from more than one angle. - Remapping possibly-active areas to look for changes. - Rolling the spacecraft around its antenna axis to view the planet at different polarization angles. - Viewing the same area from slightly different orbits to set up a "baseline" for interferometry, which might make it possible to compare phase shifts in the returned signals and do altitude measurement to millimeter resolution. This might suffice to detect tectonic movements. - Aerobraking [!] to bring Magellan down to a 300km circular orbit, giving higher mapping resolution and better gravity measurements. This will be a dicey procedure because Magellan was not designed for it, and there are also possible thermal problems with the lower orbit (since there is a lot of reflected sunlight from Venus's clouds). Aerobraking will not be tried until everything else of major interest has been done, meaning the fourth or fifth cycle at the earliest. Magellan is experiencing various minor problems [some of which may have contributed to the later troubles] but is basically healthy. The solid injection motor behaved perfectly, and fuel consumption for attitude control during the injection burn was lower than expected. Magellan's fuel supply should suffice for 10 years or more [well, this will be revised downward a bit because of some of the gymnastics during the troubles]. The Pioneer Venus orbiter tried to photograph the injection burn using its ultraviolet polarimeter, but the rocket plume wasn't bright enough to be visible. China launches first Long March 2E, the heavy-lift configuration that will be used for the Aussats. Payload was a small Pakistani research satellite and a "simulated satellite" believed to have been mostly ballast to simulate an Aussat launch. Picture of shuttle orbiters passing in the night :-), as Columbia rolls out the pad past Atlantis, parked outside waiting for Columbia to clear a VAB bay. Atlantis suffered minor tile damage due to a hailstorm during the wait, but it should be possible to re-glaze the affected tiles without removing them. Japan's Insitute of Space and Astronautical Science decides to initiate development of an Atlas-class booster for science payloads. This will be a further upgrade of ISAS's current M-3S-2 solid booster, a design which has already had many incremental updates [and is now somewhere in between Scout and Atlas in capacity]. First flight 1994, carrying a spacecraft for VLBI radio astronomy. Launches will continue to be from Kagoshima. ISAS is planning several other astronomy and geophysics missions meanwhile, and is looking at using the M-5 for Mars/Venus orbiters and a lunar mission carrying several penetrators. The long-term plan is to develop a series of M-5-launched spacecraft, so that each major space-science discipline will have a mission every five or six years. [Resemblance of this to the Solar System Exploration Committee's "Planetary Observer" series, largely dead at the hands of NASA and Congress, is probably not accidental... It looks like the Japanese recognize a good idea when they see one.] Early development work for the lunar penetrators is already underway; three of them would be launched from a lunar orbiter. The Muses-A mission required some emergency revisions after an unexpected error in final velocity from the M-3S-2, which put the orbit rather short of the Moon. (The error was only about 50 m/s, but that's a lot out there.) The Hiten mother craft expended a fair bit of its control fuel fixing the orbit. A further problem appeared when it became clear that the Hagoromo lunar-orbiter subsatellite had experienced a transmitter failure before separation; lunar-orbit injection was confirmed instead by infrared photography (from two ground sites) of its rocket plume. Hiten has since made another lunar flyby, and will make several more before its mission ends; its primary purpose is to give Japanese engineers practice in such maneuvers. Major joint project in Japan (three government agencies and thirteen companies) is near completion of development on a reusable spacecraft meant to carry technological experiments up for long stays in low orbit. It will be launched by the third H-2, and recovered by a US shuttle mission six months later, on its first mission. (There are doubts being raised about later flights, given the high cost of more H-2 launches.) Experiments on the initial flight include various materials-processing packages, a large-space-structure deployment test, an infrared astronomical telescope, and a flight test of a magneto- plasma-dynamic thruster for possible use on future spacecraft. Several other articles on Japanese aerospace activity, long on detail and light on interest. -- Imagine life with OS/360 the standard | Henry Spencer at U of Toronto Zoology operating system. Now think about X. | henry@zoo.toronto.edu utzoo!henry
leech@bodie.cs.unc.edu (Jonathan Leech) (10/09/90)
In article <1990Oct9.062710.24278@zoo.toronto.edu> henry@zoo.toronto.edu (Henry Spencer) writes: >- Aerobraking [!] to bring Magellan down to a 300km circular orbit, Aerobraking was part of the predecessor VOIR (Venus Orbiting-Imaging Radar) proposal, however. -- Jon Leech (leech@cs.unc.edu) __@/ "The imaging team is moving from its ``instant science'' mode to a more leisurely ``fast science'' mode." - Dr. Bradford Smith, Voyager Imaging Team
friedl@mtndew.Tustin.CA.US (Steve Friedl) (10/12/90)
In Henry's AvLeak summary: > The Pioneer Venus orbiter tried to photograph [Magellan's] injection > burn using its ultraviolet polarimeter, but the rocket plume wasn't > bright enough to be visible. If NASA had decided that photographing this was important, would they have been able to arrange the insertion so that Pioneer was close enough to *surely* get the picture? Or are they in such different orbits that this was just not possible? Steve -- Stephen J. Friedl, KA8CMY / I speak for me only / Tustin, CA / 3B2-kind-of-guy +1 714 544 6561 / friedl@mtndew.Tustin.CA.US / {uunet,attmail}!mtndew!friedl "No job is too big, no fee is too big" - Gary W. Keefe