rjs@drutx.UUCP (Schiffbauer) (11/30/84)
I'm writing to start a discussion about the experiment scheduled for December 25 that will produce an artificial comet above the Earth. Recently, I read about this experiment in Science magazine. This was the first I knew of it and am surprised is isn't more publicized. Apparently, on December 25th at about 4:00 a.m. an explosion of Barium at 70,000 feet above the Earth will produce a comet-like phenomenon. Scientists plan to observe the ``comet'' and the effects that the Earth's electromagnetic field has on it. I would like to know more detail about the experiment and am hoping this discussion can shed some light (np). If you have any insight about the significance of the date, I'm interested in that too. Tell me if I'm off base, but I think this can be an interesting discussion, and I don't think it has been discussed yet (if so, just send me mail instead). Thanks, rod drutx!rjs
djb@cbosgd.UUCP (David J. Bryant) (11/30/84)
> Apparently, on December 25th at about 4:00 a.m. an explosion of > Barium at 70,000 feet above the Earth will produce a comet-like > phenomenon. Scientists plan to observe the ``comet'' and the > effects that the Earth's electromagnetic field has on it. > > I would like to know more > detail about the experiment and am hoping this discussion can > shed some light (np). If you have any insight about the > significance of the date, I'm interested in that too. > > Thanks, > rod > drutx!rjs I've seen (heard) several items that discuss this "fake comet", most notably in the December issue of Sky & Telescope (page 516), and the December issue of Science '84 (page 38). Even the local radio stations have had short news items about the "comet". The comet is, as you mentioned, a cloud of ionized barium that will be released as part of a three-nation, three satellite project called AMPTE (Active Magnetoshperic Particle Tracer Explorers). The three probes (representing West Germany, the United Kingdom, and the U.S.) were launched on Aug. 16th. The way the experiment works is that Germany's Ion Release Module (IRM) ejects clouds of barium and lithium, and the other two satellites watch and see what happens. The IRM, and the United Kingdom Subsatellite (UKS) are in an orbit with a 70,000 mile apogee, taking them out of the Earth's magnetosphere and into the solar wind on the sunward side. The released gasses quickly ionize and flow back along the solar wind, much like dumping a tracer dye into a river. While the UKS takes measurements near the gas cloud, the U.S Charge Composition Explorer (CCE) will observe from a lower (30,700 mile apogee) orbit. The purpose of the experiment is to determine what fraction of the particles in the Earth's magnetosphere (including the Van Allen belts) come from the solar wind, and how many are captured from the ionosphere. Two releases have already taken place, on Sept 11th, and again on Sept 20th. These two were from positions upstream in the solar wind, ahead of "bowshock" of the Earth. Although both releases were during periods of instability in the magnetosphere, data indicates that less than 1% of the solar wind particles are trapped in the magnetosphere. The "Christmas Comet" will come from a release on the morning of December 24th (if the "weather" is bad in the magnetosphere, the backup date is December 27th). This time, the IRM will be inside the Earth's bowshock, but outside the magnetopause. Scheduled releast time for the 2kg of barium is between 11:30 and 13:30 UT, just above the Galapagos Islands. (The Science '84 article pinpoints release time at 4:16am, Pacific Time, which is 12:16 UT.) Initially, the 100 mile-wide cloud will appear greenish, but will turn blue as the barium ionizes. The appearance will be similar to a comet with a 5 degree tail. Peak magnitude is expected to be about +2.5, making the comet visible to the naked eye for about 3-10 minutes. The release point is just west of Spica (the brightest star in the constellation Virgo), althought the comet will move rather quickly to the west north west. To see the "comet", you must be in the dark at about this time, which means west of a line that runs through Mexico City, Houston, St. Louis, and Milwaukee, and Canada's Belcher Islands (where they make all that Canadian beer). For more detailed updates, call NASA at (301) 344-0470 after December 1st. By the way, there will be another release in the Spring of 1985. This time, the IRM will be centered in the Earth's magnetic "tail" (downstream). * * David Bryant AT&T Bell Laboratories * Columbus, OH 43213 * (614) 860-4516 * . : djb@cbosgd.UUCP cbosgd!djb@Berkeley.ARPA * *
wmartin@brl-tgr.ARPA (Will Martin ) (12/05/84)
Was not this same sort of thing (a high-altitude release of a barium cloud) done many years back by means of an Aerobee or some other early research rocket, like one of those two-stagers built using a V-2 as the first stage? As I recall, the results from that were relatively unimpressive, though some feared that it would create a permanent glowing cloud that would harm astronomical observation. Will
bob@islenet.UUCP (Robert P. Cunningham) (12/22/84)
The latest word is that the West German satellite will release that barium
cloud at 0218 Hawaii Standard Time on Tuesday morning.
The glowing cloud should be about 1/6th the apparent diameter of a full
moon, and in the first minute or two will be right enough for colors to be
detectable. It should appear reddish-yellow at first, but will turn deep
blue and then gray before fading from view.
The show should last about 5-10 minutes for people observing with the naked
eye, about 20 minutes for those with binoculars.
[Hawaii should be an excellent place from which to view it ... but unless
you're already here or on the way, don't make any new plans. Most of the
airlines and essentially all the hotels are booked solid thru 6 Jan due to
an unusually-large influx of tourists this season.]
--
Bob Cunningham ..{dual,ihnp4,vortex}!islenet!bob
Honolulu, Hawaii