Cover photo is a dummy reentry craft coming down under a gliding parachute, part of a JSC/Dryden project, "Spacewedge", that is investigating use of gliding parachutes and GPS navigation for precision spacecraft landing. Dryden is flying a 4ft 150lb "generic reentry vehicle" under various sizes of commercial parachutes, with commercial GPS receivers. Landing accuracy has been 170-500ft, and the engineers say it could be consistently within 100ft with military or differential GPS. The key objective is development of autonomous-landing software that can make the final upwind flare maneuver at the right time for a gentle touchdown. [The article notes that there are several commercial groups developing similar technology, but claims that NASA is ahead of them. This claim has been disputed.] NASA's immediate interest is for cargo return, but use for manned spacecraft is not out of the question. The military is also interested, not for space but for doing precision cargo airdrops from a distance.
Letter from Wesley Moore (of Boeing) observing that the space station could be quite useful as an engineering base. He suggests adding an unpressurized hangar, where spacecraft final assembly and checkout could be done (using lightweight "indoor" spacesuits), a pressurized workshop, and a space tug.
NOAA manager Thomas McGunigal to head investigation of Landsat 6 loss. Evidence continues to indicate that the Titan booster functioned fine.
Lockheed wins two big ones: Gravity Probe B, and the "engineering, test, and analysis" contract at JSC.
Goldin, commenting on the how-healthy-is-Baikonur debate, notes that Russia has run 39 launches this year with 1 failure, compared to the US with 19 attempts and 5 failures. He does think the reports of deterioration are worth investigation, though, and is sending a NASA team to witness processing and launch of a spacecraft and generally investigate.
US government is dropping hints that it may reduce regulatory barriers to Inmarsat competing in the US domestic market, perhaps in combination with opening Inmarsat's own traditional market to competition. Not everyone is pleased. Motorola smells competition for Iridium and is complaining about having to face subsidized competitors.
The latest Progress freighter to Mir (launched on schedule 12 Oct) carried a Boeing crystallization experiment that will spent a month in free fall and come down on a Raduga return capsule. Noteworthy is that the experiment went from conception to flight in six months.
First Proton launch since the May failure successful 30 Sept.
NASA investigating the one flaw in the ACTS deployment: both the explosive charges on the retaining ring fired, instead of only one, and the result was a shower of high-velocity debris in the payload bay. Workers checking out Discovery after landing found tears in insulation blankets and assorted "dings and scratches" that will require minor repairs. Nothing important was damaged, but there was one disturbing item: at least one bit of debris penetrated the aft bulkhead near the APUs, although without doing any damage after penetration.
Russia announces a new telecommunications initiative, including expansion of internal communications by replacement of the old Gorizont satellites with new Express and Express-M birds, launch of several new GALS TV-broadcast satellites, and development work on a mobile-communications comsat system.
Michael Gibson, planning director for Britain's air-traffic system, dashes some cold water on satellite-based traffic-control ideas. He says the biggest problem is going to be getting airtight agreements on who bears legal liability when something goes wrong. He also comments that when he asked his advisors how much airways could be narrowed with satellite navigation systems, he was astonished when they said that separation should be widened! "This is due to the nature of errors in the new system as compared to traditional navigation aids. The new systems are either perfect or subject to such gross errors that they are unpredictable."
Aeronautical navsat users are making one thing clear: they want a voice in policy decisions and satellite operations before committing to widespread use of satellite navigation. They would prefer operation and control by an international civilian agency; failing that, they want binding treaties to establish the ground rules.
Plot of GPS accuracy vs Glonass accuracy. The GPS position error wanders around due to DoD's error injection. Glonass, which apparently lacks this capability, yielded a much tighter pattern with a slight offset from the true position. A combined receiver kept the tight pattern of Glonass but removed the offset. There are some problems for combined use, however. Particularly noteworthy is that GPS and Glonass use different time references -- which can be several microseconds apart -- and different models of the Earth's shape. Information about the Soviet Earth-shape models is particularly difficult to come by. Studies have generally concluded that Glonass is a bit better than GPS even if you disregard the errors injected into GPS, because Glonass's orbital pattern gives more uniform coverage.
Stanford continues to investigate the concept of "pseudolites", low-power GPS-like transmitters located at airports whose signals could greatly improve the precision of GPS for landing approaches. Experimentally measured errors are a few centimeters.
Navsys Corp. continues promoting its "Tidget" scheme for precision tracking of low-cost sensors, in which the sensor receives GPS signals and relays a compressed (but not decoded) version to a more intelligent base station. Navsys is running preliminary tests of using Tidget for precise location of sonobuoys (sonar buoys dropped by antisubmarine aircraft) and radiosondes (weather balloons), the former sponsored by the UK's Defence Research Agency and the latter by Vandenberg AFB. Navsys is estimating production sensors to weigh about 50g, take about 2W of power if run continuously (0.2W if you only need updates, say, every ten seconds, as in the sonobuoy application), and cost US$75.
Spot 3, launched 25 Sept, is carrying a BMDO/USAF experiment: POAM 2, Polar Ozone and Aerosol Measurement. (This is reportedly the second POAM to fly, but what the first flew on is not mentioned.) It measures light passing through the atmosphere at nine wavelengths during satellite sunrise and sunset, yielding data on the vertical distribution of a number of gases and particles. Data will be released to the scientific community after preliminary data reduction at NRL.
NASA DC-8 flights confirm the existence of brief flashes of light covering volumes of many cubic miles at high altitudes near and above thunderstorms. Pilots and other observers have reported seeing them for many years, but scientific interest dates from 1989, when U of Minnesota researchers accidentally recorded some of them on ground- based video cameras. Researchers at Marshall [thought I wasn't going to find a space angle in this, didn't you?] then found them on video recordings of thunderstorms taken by shuttle missions.
DoD-funded US/Russian space experiment on ICBM tracking slated for next year [now there's a report nobody would have believed five years ago...]. Utah State U and the Moscow Aviation Institute are building a small satellite, dubbed Skipper, for piggyback launch on the Molniya booster carrying India's IRS-1C into orbit late next year. Skipper will start out in a near-circular 819km orbit, whence its propulsion system will lower its perigee to 150km, and then still lower until the satellite appears to be endangered, perhaps 120km. When its overall orbit gets too low, it will be briefly maneuvered into a circular orbit, and then brought down for destructive reentry on the Kwajalein range, with data expected to stop at about the 80km mark. The point of the exercise is that repeated passes through the upper atmosphere at those low perigees will produce UV-emitting bow waves quite like those of a rapidly-climbing ICBM. Tracking of the UV emissions from the bow wave has advantages over trying to track the IR emissions of the exhaust plume, notably the low background (Earth is largely dark in UV, due to absorption by the ozone layer), the closeness of the bow wave to the missile (compared to the plume, which follows at a distance), and the fact that the bow wave is still there even with a fast-burn booster whose engines shut down early. The bow wave is poorly understood; a pair of BMDO sounding-rocket flights showed that some theoretical predictions of bow-wave phenomena were off by orders of magnitude.
The Skipper project people say that only about 10% of their problems have been technical. Technology-export issues have been a nightmare: "There are people in the various bureaucracies in Washington who simply don't have direction... Either they said they don't know what the policies are, or don't quite know how to interpret policies once they have been enunciated..." This sometimes makes aerospace contractors leery of even getting involved; the supplier of Skipper's attitude-control system didn't dare participate in a design review in September because it lacked State Dept. approval. BMDO says, however, that the situation is improving, and notes that Skipper is only about a year old (it began when Gennady Malyshev of MAI, attending the annual USU small-satellite conference last year, offered the use of the piggyback payload slot).
Belief is no substitute | Henry Spencer @ U of Toronto Zoology for arithmetic. | henry@zoo.toronto.edu utzoo!henry