NROL-77, probably a new NOSS (or maybe not)

click map to enlarge

On 9 December 2025 between 19:06 and 19:28 UTC, SpaceX will launch the classified mission NROL-77 for the NRO, from SLC-40 in Cape Canaveral. The NRO Press Kit is here.

Navigational Warnings point to initial launch into a ~49 degree inclined coasting orbit. Upon passing the descending node of that parking orbit, about an hour after launch, the Falcon 9 upper stage with payload will manoeuver into a ~63.4 degree inclined orbit, likely ~1000 x 1200 km. The upper stage deorbits at the end of the first revolution, in the eastern Pacific.

I initially briefly comtemplated a higher, more unusual orbit, at 1950 km altitude, based on the ~14 minute daily shift backwards of the launch window (as gleaned from Navigational Warning NAVAREA IV 1337). That was an overinterpretation (I blame the COVID infection I suffered the past week, it messes with the brain): the NOSS-like 1000 x 1200 km orbit is more likely and it fits the location and shape of the upper stage deorbit area well.

So this could be a new NOSS (Naval Ocean Surveillance System) duo of SIGINT satellites. Or maybe not, after the experience with NROL-85 in 2022 (see earlier blog post here) which featured only one payload, not two as is typical for NOSS missions. We'll see.

Below are the relevant Navigational Warnings, and two search orbits, one for the coasting orbit (valid untill ~1 hour after launch), the second for the payload(s). 

 

040948Z DEC 25
NAVAREA IV 1337/25(11,26).
NORTH ATLANTIC.
FLORIDA.
1. HAZARDOUS OPERATIONS, ROCKET LAUNCHING 
   091906Z TO 092010Z DEC, ALTERNATE
   101852Z TO 101956Z, 111838Z TO 111942Z,
   121824Z TO 121928Z, 131810Z TO 131914Z,
   141756Z TO 141900Z AND 151742Z TO 151846Z DEC
   IN AREAS BOUND BY:
   A. 30-50.00N 078-10.00W, 32-12.00N 077-07.00W,
      32-27.00N 076-28.00W, 32-03.00N 075-57.00W,
      31-38.00N 076-07.00W, 30-40.00N 077-57.00W.
   B. 28-39.69N 080-38.17W, 28-52.00N 080-15.00W,
      28-45.00N 080-03.00W, 28-29.00N 080-22.00W,
      28-27.61N 080-31.56W.
2. CANCEL THIS MSG 151946Z DEC 25.//

 

040904Z DEC 25
NAVAREA XII 789/25(21,22,83).
PACIFIC OCEAN.
1. HAZARDOUS OPERATIONS, SPACE DEBRIS
   1731Z TO 2200Z DAILY 09 THRU 15 DEC
   IN AREA BOUND BY
   12-02.00N 112-31.00W, 12-58.00N 114-47.00W,
   00-49.00S 120-38.00W, 01-46.00S 118-25.00W.
2. CANCEL THIS MSG 152300Z DEC 25.//

 

Search orbits:

NROL-77 PARKING                 for launch on 9 Dec 2025 19:06:00 UTC
1 70000U 25999A   25343.79583334  .00000000  00000-0  00000-0 0    03
2 70000 049.1163 258.3583 1136647 049.6536 329.5142 13.42495109    02

NROL-77 NOSS payloads           for launch on 9 Dec 2025 19:06:00 UTC
1 70001U 25999A   25343.83680556  .00000000  00000-0  00000-0 0    03
2 70001 063.4415 271.5212 0133723 213.5444 360.0000 13.42495109    02

 

image: NRO

 (with thanks to Ted Molczan for discussions)

USA 327 / NROL-85

​

The video above which I shot yesterday evening (19 April 2022) shows USA 327, the NROL-85 payload, passing over my home in Leiden, slightly over two days after it was launched. The footage was shot with a WATEC 902H2 Supreme Low Light Level CCTV camera with a Canon FD 1.8/50 mm lens fitted.

NROL-85 (see two previous posts about this very recent classified launch here and here) has now been catalogued (with orbital elements witheld) by CSpOC as USA 327, catalogue nr 52259, COSPAR ID 2022-040A. Only one object was catalogued, there was no spoof second 'debris' object entered.

As already mentioned in a recent post, the fact that there is no second object is a big surprise. We expected NROL-85 to deliver two payloads, a pair of INTRUDER (also known as NOSS, which stands for Naval Ocean Surveillance System), SIGINT satellites used for geolocating shipping on the High Seas by means of time difference of arrival of their radar/radio emmisions.

Before 2001, NOSS systems existed of three co-orbiting satellites forming a thight triangular formation. From 2001 onwards (with the launch of NOSS 3-1, the first of the Block 3 NOSS-es) , this changed into two co-orbitting satellites.

(the video below, from 30 August 2018, shows a typical NOSS pair, in this case both briefly flaring due to a favourable sun-satellite-observer angle on some reflecting part of the satellites. While operational, NOSS pairs always move this close together. The NOSS pair in question is  NOSS 3-6, the same NOSS pair into which orbital plane the new USA 327 satellite was launched).

And now, we have only one, not two, satellite launched in a NOSS-like orbit. Analysts are scratching their heads over this.

Given the strong similarity in orbit, and the fact that it was launched into the orbital plane of an existing 10-year-old NOSS pair (see previous post), NOSS 3-6 (2012-048A & P), there is clearly some conceptual link of the new satellite to the NOSS program. 

But in what way exactly? There are a couple of options:

(1) This is a new generation of NOSS/INTRUDER, (i.e. NOSS block 4-1), that needs only one satellite;

(2) This is something else, something new, but related to NOSS/INTRUDER;

(3) This was meant to be NOSS 3-9, a regular NOSS pair, but something went wrong and the second satellite was not deployed;

(4) There is a second satellite but it is small (cubesat) and not yet detected;

(5) The second satellite still has to detach from the first

 

So let us briefly comment on these various options:

Option (1) apparently, is feasible, according to some. Apparently it is possible to do TDA using just one satellite

With regard to option (2), the most interesting one, one could think of for example an optical or radar counterpart to the existing NOSS 3-6 SIGINT pair: one that images the ships geolocated by NOSS 3-6. This makes sense (and it also makes sense that the new satellite orbits half an orbit apart from the NOSS pair).

While we cannot exclude option (3), I think it is not the most likely option. The same goes for option (5): with previous NOSS launches, two objects were detected right after launch. I have no opinion on option (4).

If we look at the current orbit of USA 327 and the orbit of the NOSS 3-6 pair, we note that: 

(a) they move in almost the same orbital plane; 

(b) they currently are almost exactly half an orbital revolution apart (see illustration below); 

(c) because of the latter difference in Mean Anomaly, their ground tracks are not the same but have some distance between them.

 

click map to enlarge

Observation (c) does not entirely make sense to me. Wouldn't you want your imaging satellite to follow the same ground track as the geolocating SIGINT satellites? On the other hand: true: the footprints are large enough to cover a large overlap in ocean space from both groundtracks. But still....

Another aspect of this that does not completely make sense to me is that, if USA 327 is a technology demonstrator for a new complementary IMINT mode to the NOSS SIGINT system, then why pick a 10-year-old, nearly retired pair of NOSS satellites to test it with? Why not pick a fresher pair, so you can happily experiment away for the time to come?

But maybe, those fresher pairs of NOSS satellites are deemed more suited for when, after this technology demonstration, the truely operational system is deployed. But then again, why bother with that, just replace the technology demonstrator with the operational version and deorbit the technology demonstrator.

Questions, so many questions, and my still post-COVID impaired brain cannot make much sense of it yet...

It will be interesting to see what USA 327 does (in terms of orbital manoeuvres etcetera) the coming months.

Meanwhile, Radio observer Scott Tilley in Canada has detected the first S-band radio signals from USA 327. He reports "huge fades in signal", which is odd. From Cees Bassa I understand that the frequency in question, 2277.5 MHz, is a know frequency used during the checkout-phase of NOSS 3-x pairs.

NROL-85 observed, but is it an INTRUDER/NOSS or something else? [UPDATED]

click image to enlarge

 

Yesterday 17 April 2022 at 13:13 UT, SpaceX launched the classified NROL-85 mission for the NRO. Before the launch we widely expected this to be NOSS 3-9, a new pair of INTRUDER/NOSS satellites (see previous post), based on clues as to the orbit it was launched into. 

The orbital inclination and orbital altitude suggested by OSINT infornation on the mission were typical for NOSS/INTRUDER, and the time of launch indicated a launch into the orbital plane of the 10-year-old NOSS duo NOSS 3-6. That is a pattern we have seen before with NOSS missions: a replacement launched into the same orbital plane after 10 years of operational service.

So we expected to observe two objects after launch. 

But NROL-85 had a surprise in store: so far, we detected only one object, not the expected two!

This leads to the question: is NROL-85 a new INTRUDER/NOSS, or not?

NROL-85 was first picked up by me, from Leiden, the Netherlands, some 7 hours after launch, in late evening twilight of 17 April around 19:59 UT (21:59 CEST). It was some 2.5 minutes early on my pre-launch estimated search elset. I subsequently also observed it on a second pass two hours later.

On the first pass, I captured it photographically (see image in top of this post, showing it above the roof of my house along with two old unrelated rocket stages), using a Canon EOS 80D with a Samyang 1.4/35 mm wide angle lens (the exposure is a 2-second exposure at ISO 800). The video system I had set up captured it too, but only very briefly in a corner of the field of view. Only one object was seen, nothwithstanding that I did a photographic plane scan during quite some time.

The second pass was in the northern sky with a less favourable phase angle (so the object was much fainter than during the first pass). I captured it with the video system, and after following it for a minute or so, left the camera stationary to look for a possible second object. None was detected, either before or after the detected object.

Likewise, fellow observers from the Seesat-L list including David Brierley and Eelke Visser, detected only one object too. And Scott Tilley reports that he did not detect radio signals at the frequencies usually used by NOSS.

The absence of a second object could mean that NROL-85 is not a new INTRUDER/NOSS mission after all, but something else, although the orbit is very NOSS-like.

Alternatively, perhaps it is an improved version of INTRUDER that now needs only one satellite, rather than two.

NOSS missions once consisted of three satellites orbiting close together in a triangular formation. In 2001 this changed to two satellites. Maybe now they found a way to do it with one satellite?

The object we detected is in a 1021 x 1191 km, 63.5 degree inclined orbit (update: with a longer observational arc constraining the eccentricity of the orbit better, the new value is ~ 1008  x 1207 km). This orbit is close to the specifications given in a launch contract tender for NROL-85. Below is a preliminary initial elset based on a 5.5 hour observational arc:

NROL-85 (USA 327)
1 70002U 22999A   22108.04497945 0.00000000  00000-0  00000+0 0    07
2 70002  63.5043 123.5866 0114230 185.9890 173.9785 13.40421486    07

rms 0.024 deg

Elset update (20 April 2022): Below is the latest elset based on 114 observations by Cees Bassa, Eelke Visser, David Brearley, Andriy Makeyev and me over a two-day observational arc:

USA 327 (NROL-85)                                      1008 x 1207 km
1 52259U 22040A   22109.98456423 0.00000000  00000-0  00000+0 0    08
2 52259  63.4462 118.5572 0132890 178.9713 181.1610 13.40467640    01

rms 0.011 deg    arc Apr 17.83 UT - Apr 20.01 UT

 

click to enlarge

As a final note: the post-deorbit-burn fuel vent by the Falcon 9 upper stage used for the launch of NROL-85, which was deorbitted over the Pacific Ocean at the end of the first revolution (see map in previous post), was seen and filmed from Hawaii, showing the characteristic spiral shape:

 

(a follow-up post is here)

NROL-85: probably NOSS 3-9, a new pair of INTRUDER Naval SIGINT satellites

 

image: Wikipedia

 EDIT (15 & 16 Apr):  the launch of NROL-85 has been postponed by at least two days, 'due to technical difficulties'

EDIT (17 Apr): new launch date is 17 April 2022 13:13 UT

On 15 April 2022, at 13:41 UT (or later) according to a tweet by the NRO, SpaceX will launch NROL-85 for the National Reconnaissance Office (NRO). The launch will be from SLC-4E at Vandenberg SFB. [edit 16 Apr: launch was postponed to 17 April 13:13 UT]

NROL-85 is almost certainly a pair of NOSS satellites. NOSS stands for Naval Ocean Surveillance System; they are also known under the code name INTRUDER. If correct, the duo would become NOSS 3-9 (the 9th mission of block III). It will probably enter with the designation USA 327 in the CSpOC catalogue (with orbital elements witheld).

NOSS satellites are SIGINT satellites operated by the US Navy. They geolocate shipping on the high seas, by detecting their radio/radar emissions. They always operate in close pairs. The secondary object is usually listed (with orbital elements witheld) as "debris" in the CSpOC catalogue, but this is a ruse that fools nobody: it is a payload too that manoeuvres and keeps a careful constant close distance to the primary satellite.

Information from the launch contract tender for this launch reveals that the mission aims for a semi-major axis of  7500.5 km, an orbital eccentricity of 0.0131, an orbital inclination of 63.535 degrees and an argument of perigee of 190 degrees (i.e. perigee almost on the equator). The listed semi-major axis and eccentricity translate to a 1024 x 1221 km orbit. 

The combination of the 63.5 degree orbital inclination and 1024 x 1221 km orbit strongly points to a NOSS/INTRUDER mission. These typically have an orbital inclination of 63.4 degrees and a semi-major axis of 7485 km, values close to those quoted for NROL-85. If launch is indeed at 13:13 UT on April 17, the resulting orbital plane will be very similar to that of the existing NOSS 3-6 duo (2012-048A and 2012-048P) which was launched in 2012, as can be seen in the figure below. That also lines up with a new NOSS-launch: NOSS-pairs are typically replaced after 10 years on-orbit.

The shift in launch time with date due to the two launch postponements agree with the estimated orbital altitude and orbital plane and matches the nodal precession of a typical NOSS orbital plane.

click image to enlarge

 

The Navigational Warnings for this launch (NAVAREA IV 336/22 NAVAREA XII 228/22 and HYDROPAC 987/22) define a launch direction towards the south-southeast, and agree with the 63.5 degree orbital inclination of the launch contract tender. 

[EDIT: The first NavWarning has been corrected: I initially copied the wrong NavWarning for this post.....]

100706Z APR 22
NAVAREA XII 228/22(18,21).
EASTERN NORTH PACIFIC.
CALIFORNIA.
1. HAZARDOUS OPERATIONS 1150Z TO 1514Z DAILY
   15 AND 16 APR IN AREAS BOUND BY:
   A. 34-41N 120-38W, 34-39N 120-40W,
      34-28N 120-38W, 34-04N 120-17W,
      34-04N 120-05W, 34-19N 120-14W,
      34-39N 120-19W.
   B. 32-03N 118-53W, 32-01N 118-49W,
      30-51N 117-56W, 30-21N 117-39W,
      30-08N 117-47W, 30-11N 118-01W,
      30-32N 118-18W, 31-54N 118-53W.
2. CANCEL THIS MSG 161614Z APR 22.

100644Z APR 22
HYDROPAC 987/22(22,83).
EASTERN SOUTH PACIFIC.
DNC 06.
1. HAZARDOUS OPERATIONS, SPACE DEBRIS
   1425Z TO 1649Z DAILY 15 AND 16 APR
   IN AREA BOUND BY
   20-12S 123-30W, 19-00S 119-00W,
   33-48S 109-30W, 36-00S 114-12W.
2. CANCEL THIS MSG 161749Z APR 22.

 

I have mapped the hazard areas from the Navigational Warnings and the resulting launch trajectory in the map below (the times listed along the trajectory are in UT and for the updated launch date with launch at 13:13 UT (17 April):
 

click map to enlarge

Based on the parameters from the launch contract tender, this is my orbital estimate, valid for launch at 13:41 UT on April 15 updated for launch at 17 April 13:13 UT:

NROL-85                         for launch on 17 Apr 2022 13:13:00 UT
1 70002U 22999A   22107.55069445 0.00000000  00000-0  00000+0 0    02
2 70002  63.5350 124.8521 0131000 190.0000 291.3542 13.36458926    04

 

There is an uncertainty of several minutes in pass time in this elset, progressively so after more than one revolution, and some cross-track error is possible. But the elset should be good enough for a plane scan, taking a wide time window around a predicted pass. Be carefull not to misidentify the NOSS 3-6 duo as NROL-85. An elset for NOSS 3-6 can be found here.

If the eventual launch time turns out to be later than 13:13 UT, the elset above can easily be adjusted to match the new launch time using my "TLE from Proxy" software downloadable here.

The Northern hemisphere will see good, fully illuminated evening passes on the day of launch and the days after it, so prospects are good for a quick on-orbit detection after launch.

The Falcon 9 upper stage deorbit is over the southern Pacific, just after the end of the first revolution. The deorbit-burn might be visible from south and/or central Asia.

The launch patch (see top of this post) features a cat, with a tiger as its reflection. The NRO itself explains some of the symbolism in the patch in this way:

"In the NROL-85 patch, the 3 stars represent guidance, protection, and allegiance. The cat represents loyalty and devotion shared among our nation and partners. The tiger in the cat’s reflection demonstrates that while space can be challenging, a determined attitude helps NRO succeed in going"

Given that this is going to be NOSS 3-9, the 9th instance of the Block III NOSS generation, I wonder if the cat was inspired by the proverbial 'nine lives' of cats.

It is possible that a number of other small satellites will be included in this launch as a rideshare.

The NRO press kit for NROL-85 is downloadable here.

FOLLOW-UP POST HERE reporting the first observations of NROL-85 from the evening of April 17. NROL-85 might not be an INTRUDER/NOSS after all!

A SECOND FOLLOW-UP POST HERE, going a bit deeper into various speculations about what the NROL-85 payload might be.

[a small update to this post was made 13 April 2022 09:00 UT, adding a bit more background information]

[an error where I had initially copied the wrong text of a NavWarning into this post was corrected at 13 Apr 20:30 UT - many thanks to the anonymous sharp-eyed reader who noted it!] 

[updated April 15 & 16 to reflect launch postponements] 

[updated 17 Apr 8:45 UT with updated launch trajectory map and orbital plane diagram]

Capturing a flaring NOSS duo (NOSS 3-6)

click to enlarge

On 30 August 2018 near 20:59 UT I was imaging the NOSS 3-6 duo (2012-048A & 2012-048P) during a near-zenith pass, when they briefly flared. They were at a sky elevation of 77.5 degrees at that time.

The image above is a stack of the video frames showing the flaring spacecraft: the flare of the leading P component was captured just before it peaked (I was adjusting the camera FOV during the seconds before it), the flare of the A component was captured in its entirety. Below is the video itself from which these frames were extracted (video shot with a WATEC 902H + Canon FD 1.8/50 mm lens):





I next used LiMovie to analyse the video and extract brightness curves from the video frames, with the following results. The data points shown are 3-point averages of the raw data. small discontinuities visible in the curves are where the satellite passed a star:

click diagram to enlarge

click diagram to enlarge

The leading P component seems to exibit only one flare peak. The traling A component shows an interesting  double or tripple peak. The centroids of the peaks of the P and A component were some 6.5 seconds apart.

In the diagram below, I have transposed both curves on each other by shifting the curve for the A component along both axes untill it matches that of the P component:

click diagram to enlarge

What can be seen is that the curve for the A component pre- and post-peak follows the pattern of that of the P component, but unlike the P component it shows a pronounced valley at the peak, with a small secondary peak in the valley bottom. The shape of the valley is the inverse of the peak shape of the P component. Intriguing!

The rather sudden change in steepness some seconds before and after the peaks as shown by both components is interesting too. The main peak shape is slightly asymmetric.

One option for the difference in the shape of the curve for the A component (i.e. for the "valley"at the top) might be the presence of a rotating component interfering with the flare pattern caused by the satellite body, perhaps.

NOSS (Naval Ocean Surveillance System) satellites are SIGINT satellites operated by the US Navy to locate shipping, based on geolocation of the ship's radio emissions. They are also known by the code name INTRUDER. They always operate in close pairs, such as can be seen on the video.

The P component peaked at 20:59:11.85 UT (Aug 30, 2018), at position RA 313.222 DEC +45.628. The A component has a first major peak at 20:59:17.33 UT at RA  313.331 DEC +45.077; the small secondary peak at 20:59:18.37 UT at RA 313.765 DEC +45.307; and a third major peak at 20:59:19.33 UT at RA 314.170  DEC +45.518. The two major peaks are 2.0 seconds apart.

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.

click image to enlarge

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:

click diagram to enlarge

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

click diagram to enlarge

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.

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

click image to enlarge

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.

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.

Chasing the new NOSS 3-7 pair (the NROL-55 payloads)

NOSS 3-7 (NROL-55) payloads on 2015 October 10, two days after launch
Click image to enlarge

On October 8th 2015, an Atlas V rocket launched the National Reconnaissance Office's NROL-55 mission from Vandenberg AFB. The mission consisted of two NRO payloads and a number of cubesats hitching a ride. The two NRO payloads (of which only one is acknowledged, the other being catalogued as 'debris', which it isn't) are a new NOSS pair, NOSS 3-7, which replaces the 10-year-old NOSS 3-3 duo (2005-004A and C).

NOSS (Naval Ocean Surveillance System) satellites operate in pairs, flying in close formation. They geolocate ships by radio interferometry observations of the ship's radio and radar signals.

Based on the launch direction and rocket used, as well as the few details published, we knew it would be a new NOSS duo, and from previous launches had an idea in what orbit they would be launched and what manoeuvering sequence would be used.

The first observations of the newly launched objects were made within a few hours after the launch, by several observers. About 1.5 hours after the launch, observers in Iran and Tibet witnessed a spectacular fuel vent by the Centaur rocket from the launch. Next a number of satellite trackers in our network observed the payloads and the Centaur rocket (e.g. here, here, and here).

I was clouded out on Oct 8. I could join in the chase and got my first look at the payloads only on the next evening on the 9th, but under poor conditions (very hazy) with the objects only marginally showing up on my imagery made with a 2.5/50 mm lens.

NOSS 3-7 (NROL-55) Centaur near Altair on 2015 October 10
Click image to enlarge

The next night, on the 10th, the sky was very clear, and I employed the 1.4/85mm lens rather than the 2.5/50mm lens. First, I imaged a pass of the Centaur rocket near 19:47 UT (image above). As is usual for the Centaur boosters from these launches, it was clearly variable in brightness due to tumbling. This can be clearly seen in the image below, a stack of five images:

NOSS 3-7 (NROL-55) Centaur, stack of 5 images showing brightness variation
Click image to enlarge

Next I observed the two payloads closely chasing each other near 19:55 UT. Like the previous evening, the leading object was clearly fainter than the following object (movement is from top to bottom in the image below, showing the two payloads crossing a part of Cassiopeia).

NOSS 3-7 (NROL-55) payloads on 2015 October 10, two days after launch
Click image to enlarge

NOSS pairs operate for about 10 years, each pair maintaining a close spatial proximity configuration of parallel orbits with one satellite just leading the other. After 10 years their mission is over and the pair loses their close spatial proximity. From previous patterns, Ted Molczan expects that the NOSS pair that is being replaced by this new launch (NOSS 3-3, 2005-004 A and C, launched in 2005) will end its mission and lose their close spatial proximity about 7-8 months from now, i.e. around April-May 2016.

click image to enlarge

The newly launched NOSS 3-7 duo is not yet at its operational orbit in its operational configuration. Based on past missions, they will continue to manoeuver the next few weeks until they reach their operational orbits (after which a check-out period will follow). This manoeuvering makes them interesting targets to follow the coming few weeks.

The image at the top of this post shows the pair of payloads (moving top to bottom through Cassiopeia in the image), with the leading object being slightly fainter than the trailing object. This is a pattern also seen with previous launches: once operational, both payloads will however be of similar brightness.

Open Question: Could US Military SIGINT satellites help to narrow down flight MH370's last location?

Please note: this post contains discussions of a highly speculative nature

Over the past days, it has become clear that the lost Malaysian Airlines flight MH370 has flown on for some 7 hours after contact was lost at 17:20 UT (March 7 UT, local March 8). This information comes from radio "ping-backs" of the aircraft's ACARS system received by the Inmarsat 3-F1 satellite, a geostationary communications satellite that is located at longitude 64 E over the Indian Ocean. These ping-backs were received hours after the last radio contact with the pilots and hours after the transponder was shut off, and indicate that the aircraft was still powered and 'alive' hours after it disappeared. A well written story at the CNN website gives backgrounds on the receptions and the system.

Position and footprint of Inmarsat 3-F1
click image to enlarge

In this post, I will briefly summarize how Inmarsat 3-F1 detected the aircraft and determined a wide arc where the aircraft could have been at that time. I will then explore whether additional signal receipts by classified US Military Signals Intelligence (SIGINT) satellites might perhaps have been possible. If such additional receptions exist (an open question!) they would enable to further narrow down the location of the last ping-back.

That will largely be a theoretical exercise, as so far there has been no word that the US SIGINT satellite constellation did detect these ping-backs. This post therefore entails a clear element of speculation, and the central question remains an explicit open question.


Backgrounds: 'Marco Polo' between an aircraft and a satellite

Someone in the aircraft shut off the radar transponder beacon and the active ACARS messaging system near 17:20 UT. Yet this did not fully disable the ACARS system. The system kept answering periodic "pings" by the Inmarsat 3-F1 (1996-020A) satellite. These "pings", basically a kind of "Marco?" message,  are periodically sent out by the satellite and when received by the aircraft ACARS antenna, the aircraft pings back a brief "handshake" basically saying "Polo!". While such a handshake does not contain clear information about where the aircraft is when the active ACARS is disabled, it does contain the aircraft ID.

According to press reports, the last ping-back from flight MH370 was received 7 hours after the flight disappeared, near 00:11 UT on March 8. Apparently, only Inmarsat 3-F1 received these ping-backs.

From the time it took the radio-ping to travel from Inmarsat 3-F1 to the aircraft and then back again, the distance (but not direction) of the aircraft to the satellite can be determined. For example, at a radiowave speed of 300 000 km/s, a time difference of say 0.2 seconds between Inmarsat sending the ping and receiving the answer back, indicates the aircraft is at a distance of 30 000 km from the satellite.

Once you know the distance, you can draw a globe with that radius around the location of the Inmarsat satellite. Where that globe cuts the earth surface, it creates a circle, centred on the sub-satellite point. The aircraft must have been somewhere on that circle. This is basically how the wide arc that has been published was constructed, an arc which runs from Thailand to Kazakhstan in the north, and Indonesia to Australia and the Indian Ocean in the south. The aircraft could have been anywhere on that big arc, an area stretching thousands of kilometers.

To pinpoint the aircraft more accurately to a particular spot in the arc, one needs a detection by a second and preferably a third satellite.


Could US SIGINT satellites provide additional receptions for these pings?

One source of such additional ping-back signal receptions, in theory could be one of several Signals Intelligence (SIGINT) satellites employed by the US military. Please note that I say IN THEORY as the US government hasn't provided any statements that they did (which might indicate that they didn't). In other words: I am speculating on an open question here.

It depends on a lot of factors, not the least of which are questions whether these satellites were listening at the time, and whether they were monitoring the particular VHF/UHF radiofrequencies in question. Those are questions I do not have the answers to. What I will do, is discuss which US military satellites could potentially have received these ping-backs because they had coverage of the area.

1. The Mentor and Trumpet SIGINT satellites

Two US SIGINT systems in high orbits cover(ed) the relevant area: (1) several of the very large Mentor/Advanced Orion SIGINT satellites in geostationary orbit: and (2) one of the SBIRS/TRUMPET combined SIGINT and SBIRS satellites which moves in a Highly Elliptical Orbit and hovered high above the northern hemisphere at the time.

These SIGINT satellites serve to eavesdrop on radio communications including satellite- and mobile telephony, missile telemetry and signals from groundbased and airborne radar systems.

USA 184 TRUMPET imaged on 25 Aug 2009 by the author

 Mentor 4 imaged on 18 Nov 2012 by the author

The TRUMPET satellite in HEO which had coverage of (a part of) the area at that time is  USA 184 (2006-027A). The geostationary Mentor satellites covering the area are Mentor 1, 3, 4, 5 and 6 (1995-022A, 2003-041A, 2009-001A, 2010-063A and 2012-034A).

Position of various Mentor satellites and TRUMPET USA 184

Mentor satellite footprints

USA 184 area coverage and footprint detail
click image to enlarge

2. NOSS (Naval Ocean Surveillance System) SIGINT satellites

Apart from the Mentor and Trumpet SIGINT satellites in high orbits, the US also operates a series of SIGINT satellites with accurate geolocalization capabilities in a Low Earth Orbit. It concerns the US Navy Naval Ocean Surveillance System (NOSS) satellites, of which there are several. They operate in close pairs, orbiting at an altitude of about 1000 x 1200 km in 63 degree inclined orbits. Their main purpose is to locate and track shipping through the radio communications of the latter.

A NOSS duo (NOSS 3-4) imaged by the author on 29 Jan 2011

Two duo's of NOSS satellites were covering the northern half of the area at the time of the last ping-back received by Inmarsat 3-F1: the NOSS 3-5 and NOSS 3-6 duo's (2011-014A and B and 2012-048A and P).

The NOSS 3-6 duo had the best coverage, which includes the full northern arc from Thailand to Kazakhstan determined by the Inmarsat reception:

click images to enlarge

position of the NOSS 3-5 and NOSS 3-6 duo at the time of the last pingback

in 3D: yellow arc is where the aircraft could be according to the Inmarsat 3-F1 reception

Chinese SIGINT

China operates a satellite system similar to the US NOSS, consisting of three satellite trio's in the Yaogan series (Yaogan 9A, B, C; 16A, B, C; 17A, B, C). None of these however had coverage of the relevant areas in the Indian Ocean, central Asia or southern Eurasia at that time.

Coverage summary

From the brief satellite coverage analysis summed up above, it seems that the northern overland arc from Thailand to Kazakhstan was potentially well covered by various US military SIGINT satellites: five Mentor satellites, a TRUMPET and a NOSS duo. The southern Indian Ocean arc is slightly less well covered (no TRUMPET or NOSS coverage) but was nevertheless in view of several geostationary Mentor SIGINT satellites.

The question now is: could one or more of these SIGINT satellites have captured the same ACARS ping-backs received by Inmarsat 3-F1? If so, the combination of their data with the Inmarsat data could potentially narrow down the last known position of the aircraft considerably.

It all depends on whether the satellites in question were actively listening at that time, and moreover, whether their monitoring includes the radio frequencies in which the ACARS ping-backs of flight MH370 operated. It perhaps also includes questions like whether any signals received are all kept on file, or if some selection is made and much deemed of no interest is directly discarded.

Those are some big serious "ifs", that I simply do not know the answers to: this stuff is, after all, classified. So far, the US government has not indicated that one of their SIGINT systems did capture the ping-backs. Which might mean that they didn't, as I can't imagine that they did not check for it.

Classified SIGINT satellite positions in this post (and previous posts) are based on orbits calculated by Mike McCants, based on amateur observations communicated on the SeeSat-L mailing list.

Addendum 18 March 2014:
In my initial analysis posted 17/03/2014, I forgot to include two other and older geostationary US SIGINT satellites: the two Mercury/ADVANCED VORTEX satellites that are located over East Africa.

 click images to enlarge

It concerns Mercury 1  (1994-054A) and Mercury 2 (1996-026A). Both satellites were recently moved to a new orbital position over East Africa and are station-keeping there, indicating they are operational. Their footprint includes the area of interest, although the southern Indian Ocean arc is close to the edge of their coverage.

Mercury 1 imaged by the author on 29 Dec 2013

Brightness variability of the NOSS 3-3 Centaur Upper Stage (with video)

NOSS 3-3 is a pair of US Navy NOSS surveillance satellites launched early 2005. The Centaur upper stage of this NOSS 3-3 launch, NOSS 3-3r (2005-004B) is still orbiting earth as well. And as it does so, it is tumbling.

This tumbling is visible to an observer as a regular variation in brightness. Currently, the rocket stage brightens up every 11.4 seconds.

Below video shows the regular variation in brightness: watch it go from faint to bright to faint etcetera with an 11.4 second period. It is footage from a pass over Leiden which I filmed in the evening of March 22, using the WATEC 902H and a Canon EF 2.0/35 mm lens:

click images to enlarge

Using LiMovie, I extracted the brightness variation from the movie on a frame by frame basis, resulting in the depicted brightness profile above. Note that the tops of the curve are sharp, not rounded. It is a nice saw-tooth pattern. The integrated video frame picture shows the brightness variability nicely too.

Documenting this kind of tumbling behaviour (and notably how it changes over the years) can actually provide some valuable scientific data. A number of amateur observers specialize in these "flash observations", notably my fellow members of the Belgian Working Group Satellites (BWGS).

NOSS 3-1 A & C no longer a pair, and Lacrosse 3 is missing

On November 14th and 15th, Alan Figer from France first noted that one of the objects of the NOSS 3-1 pair (2001-040 A & C) was missing. Following up on his message, I could confirm this the next evening, using photography and video. Only one object instead of the usual close pair of two was visible:



Above is the video footage that was shot by me. What turns out to be the A-component can be seen crossing Lyra (bright star is Vega. The glow in the lower left corner is from a nearby lamp), but no C component is to be seen in this video segment (nor was it for one minute before and 3 minutes after this segment). Next, Derek Breit missed it as well in a window of 8 minutes centered on the A object pass, and so did Brad Young.

Over the past few days, two possible obervations have been made of the missing C-object, now well away from the A object, by Brad Young and Bill Arnold.

The break-up of the NOSS 3-1 pair probably means it had reached end of mission. It is interesting to see that some of the older NOSS pairs (and one trio) do still  maintain their pair bonding though..

Lacrosse 3 has gone missing - perhaps deorbitted

Another satellite, the 14 year old SAR satellite Lacrosse 3 (1997-064A) has gone missing in a more serious way. It has not been seen since early October. Several observers including me and Pierre Neirinck have done plane searches but so far, it hasn't been recovered. So it has either manoeuvered into a completely different orbit, or has been de-orbitted. If the latter is true, this possible de-orbit comes half a year after the de-orbit of Lacrosse 2 late March 2011. It leaves two remaining Lacrosses  in orbit (Lacrosse 4 and 5).