From: [email protected] (Allen Thomson) Subject: Re: Questions on "Lacrosse" signal... Newsgroups: sci.space.policy Message-ID:
Organization: Netcom Online Communications Services (408-241-9760 login: guest) References: <5ci4rh$[email protected]> Date: Tue, 28 Jan 1997 02:02:01 GMT Lines: 92 Sender: [email protected] In article <5ci4rh$[email protected]> [email protected] writes: > As I posted earlier, I'm having doubts as to having this Lacrosse >business figured out. It would be just *too* fun if they were >masquerading her as a DMSP or some such thing. But now I am thinking, >shouldn't we know a whole lot more about the dang thing? > > If it is a radar imagery satellite, then presumably it has a >radar on it (all those logic classes are paying off :-) ). The thing may >not be turned on all the time, but every time the top dogs wanted a peek >at something they would have to crank her up. I guess my question is: >Does anyone have any data on any signals coming from any suspected >Lacrosse satellite? Has anyone collected it, be they a mad scanner on a >quest or an even madder scientist who thought for a moment he was in line >for a Nobel in radio astronomy? [snip] I'll be doing a bit of homework and arithmetic to prepare a set of responses and semi-responses to your question, but in the meanwhile I'm going to append a message I originally posted on 10 Jan 1997 to s.s.p. and some other groups, but which seems to have made it only to sci.military.moderated (my ISP's Usenet competence was particularly low at the time). The message is relevant because it contains what appears to be an indication that the resolution of LACROSSE is better than commonly believed. The resolution depends inversely on both the bandwidth of the signal (for range resolution) and the target time-in-beam (needed for integration to form the synthetic aperture for along-track resolution). BTW, a good, simple source on how to do SAR calculations is "Spaceborne Radar Remote Sensing: Applications and Techniques" by Charles Elachi, ISBN 0-87942-241-6. ------------------------------------------------------------------------- reposted message After admiring the latest Nikolayev shipyard picture at http://www.fas.org, I happened to look at the NIIRS (National Imagery Interpretability Rating Scale) document (*) there, and noticed something interesting. Although most of the examples in the NIIRS tables (**) are of generic (or mobile) things that might be imaged by any of a wide variety of systems, several aren't. To wit, NIIRS Sensor Illustrative Capability 2 Infrared Identify an SS-25 base 2 Radar Identify large phased array radars (HEN HOUSE, DOG HOUSE) 3 Radar Detect stuff at an ABM fixed missile site 4 Visible Detect an open missile silo door 4 Radar Distinguish between open and closed missile garage roofs 4 Infrared Detect thermally active SS-25 MSVs in garrison 5 Visible Distinguish between SS-25 TELs and MSVs at a known base 5 Radar Detect missile support equipment at an SS-25 RTP 6 Radar Identify SS-24 launch triplet at a known location 7 Visible Detect details of [SS-18] silo door hinges Now, AFAIK, these illustrative objects exist only in the interior of the FEE, and are accessible only by satellite (absent "Aurora"). So, unless the Itek (***) authors were just kicking back and fantasizing about what imaginary systems might do against semi-imaginary targets, the tables seem to provide some evidence in support of the widely-held belief that the US has not only visual but also infrared (IR) and radar imaging systems on its spysats. It also provides some upper (big is bad, small is good) bound on their resolutions. The 0.20 - 0.40 NIIRS 7 for visible systems isn't surprising, as the common lore is that KH-11 and descendants can do a decimeter quite handily. The radar figure of 0.40 - 0.75 is interesting, since most open sources give over a meter, more often two or so meters for LACROSSE. IR at 1.5 - 2.5 m NIIRS 4 is kind of what you'd expect from a mid-IR (3-5 micron) sensor looking through the same aperture that yields NIIRS 7-8 at visible wavelengths. Again, this is in accord with the canon that son-of-KENNAN/CRYSTAL has IR capability. OTOH, it's incompatible with a 8-14 micron IR sensor, as that would require a huge primary mirror. (*) Cited as as an excerpt from "Imagery Interpretability Rating Scales" by L.A. Maver, C.D. Erdman and K. Riehl of Itek Optical Systems, Lexington, MA. Unfortunately, the hyperlink to the original document is currently broken. (**) NIIRS-2 => 4.5 - 9.0 m resolution; 3 => 2.5 - 4.5 m; 4 => 1.5 - 2.5 m; 5 => 0.75 - 1.2 m; 6 => 0.40 - 0.75 m; 7 => 0.20 - 0.40 m (***) Itek is not unconnected to the reconnaissance world.