Quote from: Ben the Space Brit on 05/04/2017 12:22 pmI'm guessing that attempting to 'stealth' a spacecraft with low-optical reflectivity material would be counter-productive as it would greatly increase the internal heating from sunlight.A black satellite introduces no huge thermal problems. It absorbs a lot of sunlight, but it's also a very good emitter, so it balances out.Another approach is to cover the spacecraft with a mirror, or mirrors, that re-direct the line of sight from Earth into space.These and other approaches are summarized in the A Stealth Satellite Sourcebook, an open summary of what is known or suspected about space stealth.
I'm guessing that attempting to 'stealth' a spacecraft with low-optical reflectivity material would be counter-productive as it would greatly increase the internal heating from sunlight.
Quote from: LouScheffer on 05/04/2017 01:01 pmQuote from: Ben the Space Brit on 05/04/2017 12:22 pmI'm guessing that attempting to 'stealth' a spacecraft with low-optical reflectivity material would be counter-productive as it would greatly increase the internal heating from sunlight.A black satellite introduces no huge thermal problems. It absorbs a lot of sunlight, but it's also a very good emitter, so it balances out.Another approach is to cover the spacecraft with a mirror, or mirrors, that re-direct the line of sight from Earth into space.These and other approaches are summarized in the A Stealth Satellite Sourcebook, an open summary of what is known or suspected about space stealth.A black satellite will appear very bright in infra-red in front of the cold space, so this is not a good way for stealth. The known stealth satellite attempts (eg LES 8 ) appear to have used the mirror concept.
Quote from: Skyrocket on 05/04/2017 03:23 pmQuote from: LouScheffer on 05/04/2017 01:01 pmQuote from: Ben the Space Brit on 05/04/2017 12:22 pmI'm guessing that attempting to 'stealth' a spacecraft with low-optical reflectivity material would be counter-productive as it would greatly increase the internal heating from sunlight.A black satellite introduces no huge thermal problems. It absorbs a lot of sunlight, but it's also a very good emitter, so it balances out.Another approach is to cover the spacecraft with a mirror, or mirrors, that re-direct the line of sight from Earth into space.These and other approaches are summarized in the A Stealth Satellite Sourcebook, an open summary of what is known or suspected about space stealth.A black satellite will appear very bright in infra-red in front of the cold space, so this is not a good way for stealth. The known stealth satellite attempts (eg LES 8 ) appear to have used the mirror concept.Researchers have used fancy materials to get radiative cooling during the daytime by enhancing the emissivity in atmospheric windows. Perhaps for stealth you could do the opposite, making a material that radiates only in the wavelengths where the atmosphere is opaque. This would allow it to cool while still being hard to spot from the ground.
Quote from: LouScheffer on 05/04/2017 03:57 pmQuote from: Skyrocket on 05/04/2017 03:23 pmQuote from: LouScheffer on 05/04/2017 01:01 pmQuote from: Ben the Space Brit on 05/04/2017 12:22 pmI'm guessing that attempting to 'stealth' a spacecraft with low-optical reflectivity material would be counter-productive as it would greatly increase the internal heating from sunlight.A black satellite introduces no huge thermal problems. It absorbs a lot of sunlight, but it's also a very good emitter, so it balances out.Another approach is to cover the spacecraft with a mirror, or mirrors, that re-direct the line of sight from Earth into space.These and other approaches are summarized in the A Stealth Satellite Sourcebook, an open summary of what is known or suspected about space stealth.A black satellite will appear very bright in infra-red in front of the cold space, so this is not a good way for stealth. The known stealth satellite attempts (eg LES 8 ) appear to have used the mirror concept.Researchers have used fancy materials to get radiative cooling during the daytime by enhancing the emissivity in atmospheric windows. Perhaps for stealth you could do the opposite, making a material that radiates only in the wavelengths where the atmosphere is opaque. This would allow it to cool while still being hard to spot from the ground.Or you could use a simpler approach... Black earth facing side, and a high emmisive/radiating surface facing away from earth.
One week after launch, and the amateur satellite observing community has not yet announced tracking USA 276.(no slight to them)It would be handy if there was a list of the intervals between launch and amateur identification for classified American/allied satellites launched in recent years.
From: Ted Molczan via Seesat-l <seesat-l_at_satobs.org> Date: Tue, 9 May 2017 17:29:25 -0400Ron asked:> Did anyone figure out what the unidentified object was trailing along with> ISS I observed on Monday Morning?Several of us have been discussing your mystery object off-list, aided by the additional information that you provided.I caution that the following is very preliminary and could prove to be without merit.It does not appear to be any object that we know. NROL-76 launched into a plane that was in the vicinity of ISS. Itprobably did not target the orbit of ISS, but as Cees Bassa pointed out, since ISS is a popular target, its closeproximity to that orbit could result in serendipitous sightings.If your mystery object is related to NROL-76, then its plane is quite a bit west of where it would have been expected,based on the circumstances of the launch. I have been experimenting with various orbits that could fit your sighting andcorrelate with NROL-76.Something around 48 deg inclination seems to fit. To align with the RAAN of ISS would have required a large manoeuvrenear the northern or southern apex of the orbit, which appears to be within the capability of the launch vehicle, with asubstantial payload. Interestingly, the resulting orbit would have roughly matched the plane of the stage 2 de-orbittrajectory, implied by the time, location and orientation of the NOTAM co-ordinates.Below are a few approximate orbits that closely approximate your sighting: 328 X 335 km1 74401U 17128.36666670 .00000000 00000-0 00000-0 0 082 74401 48.0000 230.8000 0005000 209.7698 205.8000 15.80000000 08 357 X 363 km1 74402U 17128.36666669 .00000000 00000-0 00000-0 0 072 74402 48.0000 231.2000 0005000 209.7698 205.4000 15.70000000 09 412 X 418 km1 74403U 17128.36666668 .00000000 00000-0 00000-0 0 072 74403 48.0000 231.9700 0005000 209.7698 204.3674 15.50980000 04The 74401 orbit would have been near eclipse at the time of your sighting, so it is the approximate lower bound ofaltitude.I am far from confident that your mystery object is related to NROL-76, but it seems a possibility.Ted Molczan
The following elements are derived from Leo Barhorst's observations of early 2017 May 24 UTC:USA 276 398 X 401 km1 42689U 17022A 17144.06548369 .00000000 00000-0 00000-0 0 022 42689 49.9572 164.5366 0001907 186.7642 173.3300 15.56136012 06Arc 20170524.02-0524.08 WRMS resid 0.044 totl 0.009 xtrkThe arc is short, so this solution is approximate, but it should be adequate to reacquire the object tonight andtomorrow.Ted Molczan
Since Star One asked on the updates thread and immediately got thumped. Here is Ted Molczan's TLE from Leo Barhorst's data. Star One, go up one post and you can compare the search TLE's with the current rough TLE.http://www.satobs.org/seesat/May-2017/0112.htmlQuoteThe following elements are derived from Leo Barhorst's observations of early 2017 May 24 UTC:USA 276 398 X 401 km1 42689U 17022A 17144.06548369 .00000000 00000-0 00000-0 0 022 42689 49.9572 164.5366 0001907 186.7642 173.3300 15.56136012 06Arc 20170524.02-0524.08 WRMS resid 0.044 totl 0.009 xtrkThe arc is short, so this solution is approximate, but it should be adequate to reacquire the object tonight andtomorrow.Ted Molczan
Thank you for that's most helpful. Sounds more optical reconnaissance than radar in that kind of orbit.
Quote from: Star One on 05/24/2017 02:59 pmThank you for that's most helpful. Sounds more optical reconnaissance than radar in that kind of orbit.We are also assuming it is looking down or doing something we already understand...
You think it's a technology demonstrator for something else then.
Quote from: Star One on 05/24/2017 04:48 pmYou think it's a technology demonstrator for something else then.Honestly, the only thing (DOD related) that has gone to a similar orbit is the X-37 and for some reason, I doubt it's an X-37.
Quote from: kevin-rf on 05/24/2017 05:26 pmQuote from: Star One on 05/24/2017 04:48 pmYou think it's a technology demonstrator for something else then.Honestly, the only thing (DOD related) that has gone to a similar orbit is the X-37 and for some reason, I doubt it's an X-37.Interesting. Is it possible a previous X-37 flight carried the technology demonstrator in its cargo bay and now they have launched the real deal to a similar orbit?
Quote from: Star One on 05/24/2017 02:59 pmThank you for that's most helpful. Sounds more optical reconnaissance than radar in that kind of orbit.Optical recon is usually in a sun synchronous orbit, for good lighting conditions. This one is not sun synchronous. It is not in an orbit typically used by optical or radar recon, by ELNIT, by weathersats, by milcomsats, etc. The only thing it reminds me of, besides the obvious X-37B type experimental orbit, are some of the early Orbcomm store and forward (packet data relay) satellite orbits - but you need a fleet of satellites to make such a system work. - Ed Kyle
It would be very amusing if the NROL-76 payload actually was another X-37 mission.