Saturday, 27 May 2017

The range of North Korea's Hwasong-12

Hwasong-12 launch. Source: Rodong Sinmun

On 13 May 2017 at 20:58 UT (May 14 in local time, just after local sunrise), North Korea launched a new type of IRBM, the Hwasong-12. It is probably one of the surprise mobile launcher missiles seen during the April 15 parade. A North-Korean Rodong Sinmun communique on the launch is here.

Hwasong-12 on mobile launcher. Source: Rodong Sinmun
In this blogpost, I try to find the maximum range of this missile, going from released information about the missile's trajectory by Western and North Korean sources. I should ad that my analysis is not original: it is inspired by earlier similar analysis by David Wright on the All Things Nuclear blog and a later analysis by Ralph Savelsberg on the 38 North blog.

Hwasong-12 being erected. Source: Rodong Sinmun

My analysis was sparked by three things. One was that I wanted to see whether I could reproduce David Wright's results. The second was that I wanted to visualize the situation (I am a visually oriented guy).

The third was a recent exchange on Twitter between me and Dutch science journalist Martijn van Calmthout of the Volkskrant. He had written a newspaper piece on North Korea's recent missile and atomic activities that seemed to underplay the significance of the May 13 test, choosing wording to suggest North Korea could not reach Japan with this missile. I then pointed him to David Wrigth's analysis.

Van Calmthout is a good journalist, so as a result of our Twitter conversation he actually followed up with a new Volkskrant piece where he corrected himself later:

As pointed out by David Wright, the May 13 test missile was not launched on a standard trajectory but on a so-called 'lofted' trajectory: North Korea released info that the missile travelled a ground distance of 787 km and reached an apogee altitude of 2111.5 km. Western military sources quote similar figures, so I see no reason to doubt them.

Such a lofted trajectory brings the missile very high and shortens the ground track. Fired on a more normal trajectory, the same missile with the same impulse would fly a much larger ground distance. A more normal apogee altitude for a missile like this is 600 to 1300 km.

The reason that North Korea choose this 'lofted' trajectory, is in order to avoid that the missile overflies neighbouring countries, which could be mistaken for an attack and might evoke countermeasures. South Korea, Japan (for obvious reasons) don't like it when North Korea fires a missile over their territory.

The 13 May test missile was launched from Kusong in the western part of North Korea, into an E-NE direction overflying North Korea and then onwards over sea. As part of the photographs released by North Korea after the test, an image was released showing Kim Jong Un with a map of the missile's trajectory. Based on that map, I estimate the impact point of the missile to be near 41.64N, 134.27 E, which indeed is ~787 km from Kusong (I have taken the airport near Kusong as the launch location). This is a bit further away from Vladivostok than earlier reports suggested: about 250 km. Of course these could perhaps be the intended test results rather than  the true test results.

Kim Jong Un with map (click to enlarge). Source: Rodong Sinmun
blow-up of part of previous picture

I used these parameters (estimated impact point, 2111.5 km apogee altitude) as input in STK in order to model the trajectory. It suggests that the missile delivers an impulse of 5.59 km/s. The launch was towards azimuth 72.5 degrees under an angle of 81 degrees, almost vertically. The resulting time of flight would be 28 minutes, very close to the ~30 minutes reported by western sources.The resulting trajectory is (as it should be) very similar to that on the photographs above.

Next, I used the same parameters (in terms of impulse), but with the launch angle adjusted from 81 degrees to 45 degrees, consistent with a more normal trajectory optimized for maximum range. This is the visualized result:

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The red line shows the 'lofted' trajectory from the May 13 test. The blue line shows the trajectory the same missile with the same impulse would travel using a 'normal' launch angle.

The resulting maximum range I get is about 4200 km (with an apogee altitude at ~1300 km) - close to Wright's original figure of 4500 km, somewhat less than his later revised figure of ~4800 km, and slightly larger than Savelsberg's 3700 km. Given the uncertainties, all results mentioned are in the same ballpark figure.

A distance of 4200 km brings this area into range of the Hwasong-12:

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This range circle reconstructed for the Hwasong-12 includes Japan, almost the whole of China, east Russia and the Phillipines. The US bases in Guam would also be in reach, i.e. this means that in theory (and if North-Korea has developed a working re-entry vehicle to match the missile - interestingly, their Rodong Sinmun communique mentions that the test also verified "the homing feature of the warhead under the worst re-entry situation") North-Korea would have the power to strike US bases outside of South Korea with this missile.

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Outside of Hwasong-12 reach would remain Hawaii and the US mainland: the 4200 km range falls just short of reaching Alaska.

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Edit:  The actual range of a missile depends on several parameters. One of these is what you put on it, i.e. the warhead used.

The STK analysis is also slightly simplified as it treats it as purely ballistic and ignores atmospheric drag during initial launch phase and reentry.

Friday, 26 May 2017

Brightness variation of USA 276 (NROL-76)

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Last night was very clear again. I observed two passes of the new USA 276 (2017-022A) satellite, also known under its NRO launch number NROL-76. It was launched early this month by SpaceX, and I wrote in detail about this mystery payload in my post from yesterday.

The image above, taken with a Canon EOS 60D and EF 2.0/35 mm lens, shows the satellite passing over the roof of my house during the first pass (00:36 local time, 22:36 UT). It was bright and an easy naked eye object at mag +2.5 near culmination.

During the second pass, 02:06 local time (00:06 UT) it was somewhat fainter, mag +3 to +3.5, but still visible naked eye. Below are two images from this pass:

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During this second pass, I visually seemed to note some brightness variation, notably after culmination.

Analysis of the pixel brightness of the trails in my imagery seems to confirm this. They show an irregular brightness variation, notably in the third image (the last of the images above), that looks like it is a combination of several periods.

The diagrams below show the curve obtained from 4 images, and a detail curve of the third image where brightness variation seems most pronounced. Pixel values of the trails were measured with IRIS.

click diagram to enlarge

click diagram to enlarge
This variation could hint at some form of spin stabilization, or alternatively the presence of some rotating element perhaps.

I did not note this variation during earlier passes, so  it could perhaps strongly depend on the viewing angle.

Thursday, 25 May 2017

Observing USA 276, the odd NROL-76 payload

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The image above shows USA 276 passing over the roof of my house last night. USA 276 is the mystery payload of the May 1 SpaceX NROL-76 launch from Cape Canaveral.

Also visible in the image are three rocket boosters: the r/b of the classified Milstar 3 launch, and two Russian objects. Skies surely are crowded these days...

The photograph above was shot near 3:07 local time (1:07 UT) during the second of two consecutive passes. During the first pass, near 1:30 local time (23:30 UT), I obtained this video record:

USA 276 was quite faint during the first pass (I could not see it by naked eye from Leiden town center). During the second pass it was brighter, attaining mag. +3 near culmination, visible to the naked eye without problem. Due to its low orbital altitude it was very fast: the object is in a 389 x 409 km, 50.0 degree inclined orbit.

After its May 1 launch, there was a lot of discussion among our observers. The launch azimuth seemed to suggest a 50 degree orbital inclination. That would be odd (see below), so not everybody was willing to believe this. Some suggested a dog-leg manoeuvre towards a 63.4 HEO orbit. Because of the lack of precedent, orbital altitudes could only be guessed, making a quick recovery by observers more troublesome.

It took a while (23 days) before the payload was finally observed and the orbit could be confirmed. On May 23-24, the night before I obtained the imagery above, Leo Barhorst in the Netherlands finally found the payload. And it was in a 50 degree inclination, 389 x 409 km Low Earth Orbit.

The purpose of this payload in this odd orbit is a bit of a mystery. The orbital inclination of 50.0 degrees does not match common orbital inclinations attached to specific functions: US military radar satellites (ONYX, TOPAZ) tend to be in 57 degree LEO orbits or their 123 degree retrograde equivalents; SIGINT sats in 63.4 degree orbits (either LEO or HEO); optical reconnaissance satellites in 98 degree sun-synchronous LEO orbits; the X-37B space plane was in a 39-degree inclined very Low Earth Orbit. An orbital inclination of 50.0 degrees, as shown by USA 276, is odd and unusual.

The common opinion is that USA 276 is some technology demonstrator, somewhat similar to the ill-fated USA 193 from 2006, blown from the sky with a SM-3 in 2008. But what technology does it demonstrate?

click map to enlarge

Orbital inclination and orbital altitude are in fact very (some would say oddly) similar to the ISS (see diagrams above and below, showing how close the orbits currently are): the two objects in theory (and based on the current USA 276 orbit) can potentially even make quite close approaches, to within a few km (!), as Ted Molczan showed in a private communication.

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I have found that on June 4, USA 276 will in fact be very close by when (if all goes according to plan)  the SpaceX DRAGON CRS-11 should arive at the ISS at this date. That is, if USA 276 doesn't change its current orbit before then.

Observers in Europe might see the three objects close together in their evening twilight of June 3, with USA 276 some 15 degrees distant from the ISS.

The diagram below shows the position of USA 276 relative to the ISS on the European evening of June 3, if USA 276 has not manoeuvered by then:

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Due to slightly different rates of precession of their orbital nodes, the orbits will slowly diverge from their current close coincidence over time, unless USA 276 makes a corrective manoeuvre.

I have pondered the question whether this all is coincidental or not. While I can in fact think of a potential goal where this all would be on purpose, that would be a very wild thing to do, so perhaps it is not so likely. For the moment, let's better chalk it up to coincidence until new developments seem to point otherwise.

Updating the changing tumble period of the USA 144 decoy

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The diagram above shows the brightness variation of 1999-028C, the USA 144 decoy, as determined on 21 May 2017. It was created from photometry on video records spanning several minutes of a pass using a WATEC 902H with a Samyang 1.4/85 mm lens. The photometry was obtained using a not-yet-public beta-version of TANGRA.

The brightness of the object shows a slow variation between mag +7.2 and invisible. Fitting a sinusoid gives a peak-to-peak period of 43.528 seconds, +/- 0.005.

I have written on this enigmatic object before on this blog. It was launched from Vandenberg 18 years ago, on 22 May 1999, as NROL-9. This launch is widely believed to have launched the second Misty stealth satellite. Following the launch amateurs found this relatively bright object in a (currently) 2668 x 3150 km, 63.4 degree inclined MEO orbit. The object shows a periodic brightness variation.

This object is, however, not Misty 2. A long term analysis by Ted Molczan showed that the object has an unusually large surface-to-mass ratio in the order of 0.09 m2/kg and its orbit is subject to considerable Solar Radiation Pressure (SRP) effects. The surface-to-mass ratio is an order of a magnitude larger than for normal satellites, suggesting this is something large and lightweight - e.g. something inflatable, so large and light that pressure from sunlight has an effect on its orbit.

We have come to believe that it is a decoy, designed to lure attention away from the real, stealthy USA 144 payload when it was launched in 1999.

As the result of SRP influence, the tumble rate is variable over time: in the order of 60-90 seconds 7-8 years ago, 50 seconds 2 years ago (see here), and now 43.5 seconds.

Saturday, 29 April 2017

What is NROL-76 and what orbit wil it be launched into?

Tomorrow, 30 April 2017, with (from the area warnings) a three-hour launch window starting at 10:55 UT, SpaceX will launch a classified satellite for the NRO. The launch is designated NROL-76 and will happen from launchpad 39A at Cape Canaveral, Florida. The press-kit is here.

There has been some speculation on what this launch might be and what orbit it will go into.

Considering the latter, Ted Molczan discussed three options in two separate SeeSat-L posts (here and here): a launch into HEO (Molniya) orbit of a new SDS satellite; a launch into GEO of a new NEMESIS; or a launch into LEO, perhaps a new version of the ill-fated USA 193 launch from 2006.

The launch azimuth deduced from the Area Warnings that appeared after Ted posted his initial speculation on the payload, narrowed the options down to two: HEO or LEO. To me, the Area Warnings strongly suggest the second option: a launch into LEO, perhaps a USA 193 follow-up.

The Maritime Area Warnings published for the launch show two hazard zones: one near Cape Canaveral, and one, with a window opening four-and-a-half hours later than the launch window, in the Indian Ocean stretching from south of Madagascar to north of Kerguelen:

NAVAREA IV 342/17 [1 of 1][[WWNWSFOLDER]]

ALTERNATE 011055Z TO 011354Z MAY
28-39N 080-39W, 30-34N 078-45W,
31-32N 077-34W, 31-26N 077-13W,
31-06N 077-11W, 30-47N 077-32W,
30-08N 078-26W, 28-29N 080-21W,
28-26N 080-27W, 28-25N 080-35W,
28-25N 080-38W.
2. CANCEL THIS MSG 011454Z MAY 17.//

Authority: EASTERN RANGE 211830Z APR 17.

Date: 271553Z APR 17
Cancel: 01145400 May 17

HYDROPAC 1447/17 [1 of 1][[WWNWSFOLDER]]

DNC 02, DNC 03.
ALTERNATE 011438Z TO 011715Z MAY
30-31S 038-04E, 30-40S 040-19E,
40-11S 060-06E, 47-31S 080-01E,
48-56S 079-46E, 49-00S 075-21E,
47-12S 063-50E, 41-51S 049-33E,
35-39S 040-15E, 32-07S 037-37E.
2. CANCEL THIS MSG 011815Z MAY 17.//

Authority: EASTERN RANGE 211827Z APR 17.

Date: 250231Z APR 17
Cancel: 01181500 May 17

I have put them in maps for your convenience:
click map to enlarge
The first area points to a launch azimuth of 43-45 degrees, indicating (if no dog-leg is involved) launch into an orbital inclination of 50-51 degrees as can be seen in the first map I prepared, above. This would at first sight exclude launch into HEO/Molniya orbit at inclination 63.4 degrees, unless of course a dog-leg manoeuvre is involved, which is possible.
click map to enlarge

The second area, in the Indian Ocean, points to the de-orbit of the upper stage about 4.5 hours after launch and actually matches a launch into an ~51 degree inclined LEO orbit as well.

In the map below, I have printed an estimated Low Earth orbit for the upper stage of the launch, based on the 2006 USA 193 orbit in terms of apogee and perigee, but with the orbital inclination changed to 51 degrees. About 2.4 orbits after launch, near 14:38 UT when the hazard warning window opens, the stage would be over Africa on its way to the hazard area, which has a position and curvature matching the trajectory (given the uncertainties in my orbit estimate) close enough, in my opinion, to accept this potential scenario of launch into an approximately 51 degree inclined, about 355 x 375 km orbit, or something similar to that:

click map to enlarge

One has to wonder though why the de-orbit is 2.5 revolutions after launch, and not simply during the second part of the first revolution. Perhaps some experiments will be done with the stage? Or does it deliver additional (small) payloads perhaps? Your guess is as good as mine.

In terms of the payload itself, Ted Molczan has posted some interesting info to SeeSat-L suggesting the payload is based on  Boeing's commercial, completely electrical thrust BSS-702SP bus.

The purpose of the payload(s?) is completely unclear at the moment. Radar satellites such as Lacrosse/ONYX were previously launched into 57-58 degree inclined orbits or their retrograde 123 degree equivalent (FIA/TOPAZ). Optical reconnaissance satellites such as KH-11 are launched in 97 degree inclined sun-synchronous orbits. NOSS (INTRUDER) SIGINT duo's are launched into 63.4 degree inclined stable perigee orbits. If this payload ends up in a 51 degree orbit, this is new.

There is a possibility that, while initially launched and inserted into a 51 degree orbit (a launch trajectory with which SpaceX is familiar from their CRS launches to the ISS), the payload next manoeuvres into a 58 degree or even 63.4 degree orbit on its own, using its electrical thrusters.

It will be interesting to see what orbit the object or objects eventually will be found in. It is likely it will be designated "USA 276".

If the 51-degree orbital inclination scenario is correct, observers in the Northern hemisphere will, unfortunately for me, not have visual sighting opportunities after launch: optical detection will rest on the shoulders of Southern hemisphere observers.

[added note 29 apr 15:15 UT] On April 30, be aware for possible re-entry sightings from Madagascar, especially the southern part of the island, near 14:40 UT, in early twilight (assuming launch at ~11:00 UT).

Wednesday, 5 April 2017

VIDEO: the ISS Fabric Shield (again), and North Korea's Kwangmyongsong-4

Yesterday I posted April 3 photographic imagery of the ISS Fabric Shield (1998-067 LF), a 1.5 x 0.6 meter anti-micrometeoroid shield astronauts inadvertently let fly into space during an EVA on March 30 (see my previous post for more details).

Yesterday evening April 4, in late twilight, I managed to film the object, which was now 1m 45s ahead of the ISS. The video, shot with a WATEC 902H low-light-level camera and a Samyang 1.4/85 mm lens, is above.

Later in the evening I also targetted  North Korea's Kwangmyongsong-4 (KMS-4, 2016-009A) which I had filmed, but as a very faint object, a week before as well. This time, KMS-4 was much brighter due to a more favourable illumination angle, and is easy to see as it cruises past Alcor and Mizar:

Both the ISS Fabric Shield and KMS-4 do not show a clear periodic brightness variation in the video imagery. The only variation that is there are slow trends (altitude and illumination angle related) and fluctuations within the fluctuation expected from atmospheric scintillationand oscillations in the video signal (estimated by looking at variations in the apparent brightness of a comparison star) :

click diagram to enlarge

Monday, 3 April 2017

The ISS Fabric Shield accidentally released from the ISS imaged in orbit

On March 30, 2017, NASA astronauts Shane Kimbrough and Peggy Whitson conducted an EVA from the International Space Station to prepare a new docking port and install new equipment on the outside of the ISS.

click to enlarge

During this spacewalk, they accidentally released a 1.5 x 0.6 meter large protective Fabric Shield, a shield against micrometeoroids that was one of four to have been installed that day on one of Tranqility module's ports. Somehow it got loose  and floated away in space, before the astronauts were able to retrieve it. Oopsy!

Once floating free in space, and having become space debris, it was catalogued by JSpOC as object nr. 42434, 1998-067LF.

The image above shows the shield, imaged from Leiden last night during a zenith pass with an 1.4/85 mm lens. It is faint and was almost exactly a minute in front of the ISS. It seemed steady in brightness on the 3 images I obtained (spanning an arc of 15 seconds in time).

Here is a screencap of the moment the object floated away during the EVA, somehow having come loose of its tether:

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The image below shows the ISS, a minute later (bright stars are kappa and iota UMa):

The accidentally released Fabric Shield has a relatively large surface relative to its weight [added edit: it weights 8 kg and measures 1.5 x 0.6 meter], which means it will quickly decay and re-enter, probably within 5 to 6 months from now.

Thursday, 23 March 2017

NOSS 3-8 (NROL-79) components now close to operational separation

In a recent blog post I documented the intricate manoeuvering of the two NROL-79 payloads (NOSS 3-8) over the past three weeks. They were manoeuvering to circularize and synchronize their orbits and manoeuvre to a desired mutual distance.

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Much of this manoeuvering is now done, and the two spacecraft are now flying in formation at a mutual distance of ~50.5 km. They now look like a typical NOSS pair, as can be seen in the image above shot in the evening of March 21 (the bright star is Procyon).

Below is an updated diagram, showing the evolution of the separation between the two spacraft over time:

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After an initial rapid post-launch separation with a drift of ~31-32 km/day, reaching a maximum separation of ~202 km on day 6 after launch, the separation distance started to decrease post day 6, and is now, by day 20-21 after launch, clearly flattening out to a stable separation distance of about 50 km.

The Mean Motion/orbital period of the two spacecraft are now very similar too, as is their orbital inclination: all signs that they are now close to the desired configuration. The two orbital planes are currently about 0.2 degree separated in RAAN.

click diagram to enlarge
click diagram to enlarge
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While they are now at their operational distance (which looks to be ~50 km in this case) and close to operational configuration, this does not mean that NOSS 3-8 is now fully operational. Over the coming weeks, they will probably undergo extensive check-out tests. I also expect them to continue to make small manoeuvres for a while (but while maintaining a more or less stable mutual distance at ~50 km).

Several amateur satellite trackers contributed data to this analysis, including Leo Barhorst, Cees Bassa, Russell Eberst, Alain Figer, Paul Camilleri, Dave Waterman, Alberto Rango, Brad Young and me.

Sunday, 19 March 2017

NOSS 3-8 (NROL-79): Dancing in the Dark

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The image above shows the new NOSS 3-8 duo (2017-011 A & B, launched as NROL-79 on March 1, see my earlier blog post here), aka USA 274, imaged on March 12 through very thin cirrus.

Over the past 2.5 weeks a number of us (Leo Barhorst, Cees Bassa and me in the Netherlands; Russell Eberst in Scotland; Alain Figer in France; and Paul Camilleri in Australia) have been chasing this duo and monitored their manoeuvering, consisting of small adjustments in apogee and perigee and orbital period.

Click diagram to enlarge

I expect their manoeuvering to be complete by 21 days (3 weeks) after launch, i.e. near March 23. They will then have attained their finalized separation distance. I expect this initial operational distance to be about 45 km. I do not exclude further small manoeuvres after March 23 though, but these will be more as a pair, and not with respect to each other.

NROL-79 consists of a NOSS (Naval Ocean Surveillance System) duo: two payloads orbiting as a close pair (typically 30-55 km). The second object is  catalogued as "debris" by JSpOC (they did this with all second payloads of NOSS launches), but isn't: after all, real debris shouldn't manoeuvre, and shouldn't stationkeep with respect to the other payload.

click diagram to enlarge

After insertion in a 1010 x 1204 km, 63.45 degree inclined orbit, the two payloads started an intricate dance in space, step by step positioning themselves with respect to each other.

In the initial week after launch the two payloads separated at a rate of ~31-32 kilometer per day, to a maximum separation of just over 200 km on Day 7. Then their drift reversed, with the two payloads gradually moving closer again (see diagram above, which also gives similar data for a previous NOSS launch, NROL-55 (NOSS 3-7) from 2015). Extrapolating the drift, and looking at the previous NOSS launch, I expect that by the end of the 3rd week after lauch (~March 23, 2017) the two payloads will reach their intended separation of ~45 km, and stabilize with respect to each other.

It is interesting to note the difference with the previous NOSS launch, NOSS 3-7, also depicted in the diagram. The latter initially drifted further apart, and for a longer time: the separation increased until 14 days after launch (double as long as for the current case), to as much as ~570 km (almost three times as large as the current case), before the two objects started to move closer again.

In the image below, taken three days apart on March 10 and March 13, the decrease in distance over time after the first week can clearly be noted (in the images, movement is from top to bottom and the B-object is leading). The images show the payloads in roughly the same part of the sky (bright stars are 1, 10 and 13 Cyg):

click image to enlarge

A first major manoeuvre occurred on day 6, when both payloads lowered their orbital period:

click diagram to enlarge

Around that same date, the visual brightness of the two objects changed. The latter probably signifies the deployment of something on the payloads: either antennae, or perhaps panels used to make minor orbital adjustments by decreasing or increasing drag (it has long been rumoured that this is one of the ways the NOSS payloads maintain their bond).

The pattern between the current launch and the previous launch is similar (although I have a suspicion that for the previous NROL-55 launch in 2015, analysts switched the identitities of the two objects around day 6): a major orbital period adjustment on day 6, after which one of the payloads gradually increases its orbital period again while the other very slowly decreases its orbital period. But what can be seen is that for the current case, the values for both payloads stay much more similar than was the case with the previous launch, just as with the evolution of the spatial separation of the two. One of the things this could point to is that, perhaps, the initial orbit insertion of NROL-79 went better than for NROL-55, but this is speculation.

Note: orbital calculations for NROL-79 used were done by myself using observational data from the persons mentioned in the main text. The NROL-55 orbit calculations from 2015 were by Mike McCants and  Ted Molczan. I am indebted to Leo Barhorst and Bram Dorreman for their help in filling gaps in my archive of orbits for the latter object.

Thursday, 16 March 2017

USA 186 recovered

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The image above shows USA 186 (2005-042A), a KH-11 ADVANCED CRYSTAL ("Keyhole") optical reconnaissance satellite. It is cruising just below the Pleiades star cluster in this image, which I shot yesterday evening using the Samyang 1.4/85 mm lens and an exposure of 2 seconds.

USA 186 was recovered last week after being briefly lost in the Northern hemisphere winter blackout. Leo Barhorst made one or two possible detection in February, but it was Cees Bassa who unambiguously recovered it on March 13th. Two days later, I made the image above.

The arc is still short, but it appears to be in an approximately 265 x 435 km sun-synchronous orbit. The apogee is some 20 km lower than it previously was, the perigee is about 5 km higher (i.e., the current orbit is more circular than previous orbits). It's ground repeat interval is 4 days.

USA 186 is the secondary West plane satellite in the KH-11 constellation. The hunt is now on for USA 245, the primary West plane KH-11. Recovery of the primary East plane KH-11, USA 224, will have to wait untill early summer.

When I observed it yesterday it was bright (mag +1.5) and briefly flared to mag 0 near 19:32:50 UT (March 15, 2017).

Friday, 3 March 2017

Tracking NROL-79, a new NOSS duo

Launch of NROL-79 from Vandenberg on March 1, 17:49 UT (photo ULA)

On March 1, 2017, at 17:50 UT,  an Atlas V rocket was launched from Vandenberg with a classified (double) payload for the National Reconnaissance Office (NRO) onboard. It was the 70th Atlas V mission, and the 14th NRO launch using this launch vehicle.

The two payloads were launched towards a southern direction into a 63.46 degree inclined, 1010 x 1204 km orbit. The payloads are almost certainly a new set of NOSS (Naval Ocean Surveillance System) satellites, NOSS 3-8 (NOSS satellites are also known under the code name INTRUDER). These are SIGINT/ELINT satellites operating in close, formation flying pairs. The purpose of these satellites is to geolocate radio signals, notably signals originating from ships. In order to keep their mutual distance  stable, they operate in 63.4 degree orbits, a critical inclination which keeps perigee in a stable position.

This is the 8th launch in the third generation of these spacecraft.

Based on estimated search elements, both payloads were quickly picked up by amateur trackers. Russell Eberst in Scotland and Alain Figer in France first spotted them about 10 hours after the launch, on March 2.  Paul Camilleri in Australia soon followed. I was clouded out that night, but the next night (March 3) was clear in Leiden, and I managed to image the payloads on two consecutive passes, albeit under a somewhat hazy sky. It was also imaged by Leo Barhorst that same night.

Below are two of my images of the two payloads chasing each other, from consecutive passes, obtained from Leiden under a hazy sky (click them to enlarge):

NROL-79 payloads, image 3 March 2017, 1:43 UT (click to enlarge)

In the image above taken during the first pass near 1:43 UT, the objects are moving from top to bottom through a field in Cygnus. In the image below, from the second pass, they are moving from left to right. Note the difference in brightness between the two objects, noticable during this second pass:

NROL-79 payloads, image 3 March 2017, 3:31 UT (click to enlarge)

The NOSS components are usually designated A and B (sometimes A & C). For the moment, we have named the fainter leading object B. The objects are currently still quite faint, indicating that they have not yet deployed their solar arrays and other gear.

The B object is usually catalogued as "debris" by JSpOC, but this is a ruse: in reality it is a functional payload (as it manoeuvres and carefully stationkeeps with the A component during its operational years).

Our current tracking data established that they are in a 63.46 degree inclined, 1010 x 1204 km orbit. The two payloads are about 45 km apart in space.

Over the coming days, they will likely make manoeuvres to finalize their orbits and respective positions.

The respective distances of current still operational NOSS pairs (NOSS 3-3 to 3-7) varies between 39.5 and 55 km.