From: "Ted Molczan"
Newsgroups: sci.space.policy Subject: Re: Doubts about FAS "Lacrosse" homepage... Date: 28 Jan 1997 01:31:26 GMT Organization: Molczan Software Services Lines: 175 Message-ID: <01bc0cba$3e12c880$cb8dbfcc@molczan> [email protected] wrote in article <5ci2qk$[email protected]>... > In summary, I think that the spacecraft pictured is a SIGINT > spinner, and that some of the other data (like the orbit) don't make any > sense at all for Lacrosse. Well, they may or may not make sense, but the orbits are real, and I have never heard anyone credibly dispute the pre-launch AWST story. I do admit, however, that they have been proven to be seriously wrong on occasion. The orbital inclinations and altitudes (statute miles) shown by FAS are correct. Lacrosse 1 was deployed by a shuttle into a 57 deg, 454 km orbit, then manoeuvred about one week later to a 680 km orbit. Lacrosse 2 was launched on a Titan 4 into a 68 deg elliptical parking orbit with apogee near 680 km, and subsequently circularized. The lower inclination of Lacrosse 1 probably was a compromise, forced by the cancellation of the VAFB launches. Here are recent elements, in NORAD 2-line format, produced by hobbyists, currently accurate to about 1 s in time: Lacrosse 1 18.0 4.5 0.0 3.6 v 1 19671U 88106 B 96350.29026275 .00000025 00000-0 40676-5 0 01 2 19671 56.9770 83.5036 0002000 2.5888 357.4112 14.70730323 01 Lacrosse 2 18.0 4.5 0.0 3.6 v 1 21147U 91017 A 97 13.28495506 .00000060 00000-0 10300-4 0 09 2 21147 67.9890 193.4974 0006000 204.1088 155.8912 14.68587962 09 These objects are very bright, regularly reaching visual magnitude 2 to 3 on favourable passes. So they must be large. Also, they have a very pronounced orange-red hue, which suggests that most of their surface must be covered with gold kapton blanket. I cannot imagine a LEO ELINT of such huge size. It easily fills the shuttle's cargo bay. This has to be Lacrosse. > Satellite: This thing is a radar imaging satellite? The primary > feature appears to be a large high-gain antenna, which is identified as > the radar antenna. The problem, however, is that the state of the art in > radar imagery birds (even back when Lacrosse was designed) is the use of > an array. As a general rule, big dishes don't work out for operational > imagery. That feature has bothered me too. I have pictures of just about all of the SAR sats that have flown, and all have arrays. > Why would anyone fly an imagery bird in a classic ELINT orbit? > For starters, IIRC, the maximum latitude under the ground track will > correspond to the inclination. Since known radar imagery systems (like, > once again, our canuck cousin RadarSat) image only relatively closely > along the ground track, this orbit makes no sense. For example, > Murmansk/Severomorsk/Plesetsk are all too far north, as is most of > eastern Siberia (with its plethora of imagery favorites). Lacrosse 2's orbit seems to be current standard, which at 68 deg, does cover the far north quite well. > Oh yeah. On that last point. If it doesn't make sense to put > Lacrosse into a SIGINT orbit, then what kind of orbit would you expect it > in? How about an imagery orbit? I have speculated that the originally intended orbit might well have been sun- synchronous, and closely coordinated with the KeyHole optical imagers. One clue is that their orbital periods are nearly the same. A Lacrosse in a sun-synchronous, circular, 650 km orbit, would have the same mean nodal period as the KeyHoles, enabling synchronization, as is standard with the KeyHoles. This orbit is about 30 km lower the present Lacrosse orbit. Also, consider that the shuttle has a somewhat higher payload capacity than the Titan 4 - which would have been greater still, had the lower mass, filament-wound SRMs been used, and the SSME's allowed to operate at greater thrust, as had once been planned. So the present 68 deg VAFB-launched Lacrosse orbit may well be another post-Challenger compromise. It will be interesting to see whether or not the greater payload capacity of the new Titan 4B might be used to place future Lacrosses into sun-synchronous orbits. I understand that the next VAFB Titan 4 is scheduled to launch in April. Anyone know whether or not it will be a Titan 4B? I have said that a Lacrosse is my best guess for this launch, because both existing spacecraft are old, 6 and 8 years, respectively. KeyHole seems unlikely because the standard two-satellite constellation is very fresh, with successful launches in Dec'95 and Dec'96, and the Nov'92 payload still in orbit (as of fall'96), in an apparent back-up role. Here are the most recent orbits derived by hobbyists from their observations. USA 86 and 116 are out of date, and will not be readily visible to N. hemisphere until the spring. I do know, however, that USA 116 manoeuvred on 13 Jan, to synchronize its orbit with that of the newly launched USA 129. We have up-to-date USA 129 elements thanks to a rare visibility window at 30S to 40S latitude, where there are a few very good observers. If USA 86 has remained in its back-up orbit, then the relatively low drag ensures that its elements remain reasonably accurate: USA 86 15.0 3.0 0.0 5.1 v 1 22251U 92083 A 96278.17789870 .00000333 00000-0 22849-4 0 04 2 22251 97.7786 19.5370 0421949 272.3687 82.5935 14.54541260 01 USA 116 15.0 3.0 0.0 5.1 v 1 23728U 95066 A 96278.20161860 .00008255 00000-0 85529-4 0 00 2 23728 97.8720 27.5568 0525374 269.1337 84.6263 14.78156876 09 USA 129 15.0 3.0 0.0 5.1 v 1 24680U 96072 A 97 18.85811921 .00006385 00000-0 65978-4 0 08 2 24680 97.8745 84.2363 0552461 70.2327 255.0973 14.72378315 04 >It makes even more sense than it sounds > like. > The 'regular' optical imagery satellites are typically in "polar" > orbits that take them over places at about the same time each day. For > example, one imagery bird will be the '9 AM' another the '1PM' and the > third the '4:30 PM' (I'm just guessing these, someone can fill in some > real values). Here are the nominal times. Actual times typically are within a few minutes of the nominal times, depending on how far the orbit has drifted east or west. The western-plane, currently occupied by USA 129, makes south-bound equator crossings at 10 AM, and north-bound ones at 10 PM, local standard time. The eastern plane, currently occupied by USA 116, makes south-bound equator crossings at 1:15 PM, and north-bound ones at 1:15 AM, LST. When there has been a third KeyHole, this has always been an older sat, in an apparent back-up role, with its plane drifted somewhere between the two primary sats. As of fall'96, USA 86, which had been in the eastern plane, was the back-up, drifting westward at about 2 deg/month. Assuming it has not manoeuvred since the fall, it would now be making southbound equator crossings at 12:22 PM, and northbound ones at 12:22 AM. >This makes a great deal of sense since it doesn't work too > well to take pictures in the dark. On the other hand, the one great > advantage of a radar imagery bird is that it *can* take pictures in the > dark. The KeyHoles are believed to have night-time imaging capability. >In order to maximize its usefulness, wouldn't one expect it to be > placed into an orbit that mimics that of its compatriot optical imagery > birds, except that it arrives every time in the middle of the night? > I.E. one would expect a '2 AM' orbit or equivalent. This would allow for > periodic coverage around the clock (and managers *love* that) and would > maximize exploitation of the systems strength--the ability to do night > collection. If I were looking for a Lacrosse I would be looking for a > sun-synch orbit that comes over in the middle of the night, but that > naturally still puts the platform in sunlight for at least some part of > the day. This is worlds different than what is listed on the FAS page. Well whatever the merits of a sun-synch orbit, the current Lacrosse orbits on the FAS page are correct. However, you have raised some important issues. It will be interesting to see what happens in future. Ted Molczan Toronto