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

Imaging North Korea's new Kwangmyŏngsŏng-4 satellite, and the flash period of its UNHA-3 rb

Kwangmyŏngsŏng-4 on 28 Feb 2016
(click image to enlarge)

North Korea's recently launched new satellite (see a  previous post), Kwangmyŏngsŏng-4 (KMS-4: 2016-009A), is finally starting to make visible evening passes here at Leiden.

Yesterday evening, 28 Feb 2016 near 19:45 UT (20:45 local time), I shot the image above, one of two images showing the satellite passing near the Celestial pole. It is a short exposure of 2 seconds with the 2.8/180 mm Zeiss Sonnar lens on my Canon EOS 60D.

Below is the same image, but in black-and-white negative, showing the trail a bit better:

Kwangmyŏngsŏng-4 on 28 Feb 2016
(click image to enlarge)

The object is very faint (probably near mag +7). It needs a rather big lens (the Zeiss 2.8/180 mm has a lens diameter of 6.4 cm), which unfortunately also means a small FOV. Over the two images, a total imaging arc of ~6 seconds, it however appeared to be stable in brightness with no sign of a periodicity due to tumble. So either it is not tumbling, or if it is tumbling at all it must be a very slow tumble.

Some 16 minutes earlier, near 19:28 UT, I also imaged the upper stage of the Kwangmyŏngsŏng/UNHA-3 rocket (2016-009B) that was used to launch the satellite. This object is brighter and shows a nice tumble resulting in periodic flashes. Below are crops from three images spanning 19:28:32 - 19:28:44 UT. The brightness variation is well visible (the bright star it passes in the first image is beta Umi):

brightness variation of UNHA-3 r/b 2016-009B on 28 Feb 2016
(click image to enlarge)

A fit to the measured brightness variation over these three images shows several specular peaks at regular intervals, with a slightly asymetric profile:

click diagram to enlarge

The fit shown in red is the result of two combined sinusoids: a major period of 2.39 seconds with a minor period of 1.195 seconds superimposed (resulting in the slight asymmetry). Pixel brightness over the trails was measured with IRIS. The data were fitted using PAST.


UPDATE 1 March 2016:

I imaged both the UNHA-3 r/b and Kwangmyŏngsŏng-4 again in the evening of 29 Feb 2016. The sky conditions wer less good, and the pass was much lower in the sky. I used the 1.4/85 mm SamYang lens this time, to get a larger FOV in order to try to capture a larger arc.

KMS-4 was captured on four images (2 second exposures) between 19:19:17 - 19:19:34 UT. It was barely visible on the images, but again the brightness appeared to be stable over this 17 second time span.

The UNHA-3 r/b was also captured, and 3 images (5 second exposures) between 18:58:42 - 18:59:07 UT again showed a very nice flash pattern, fitting (like the observations of Feb 28) a flash period of 2.39 seconds:

click diagram to enlarge

The image below is a stack of these three images. The rocket stage moves from upper right to lower left in the image.

Inconsistent DPRK versus JSPoC orbit claims for Kwangmyŏngsŏng 4

This post is a brief update to my more elaborate post of earlier today here.

As I wrote in that post, western military tracking of the N-Korean satellite places it in an orbit with perigee at 465 km, apogee at 502 km and an orbital inclination of 97.5 degree.

It is interesting to compare this with the (English) radio announcement of the DPRK itself, which you can hear here.

In that bulletin, the orbit is given as having perigee at "494.6 km", apogee at "500 km", and an orbital inclination of "97.4" degrees.

Compare this to JSpOc data: 465 km, 502 km, 97.5 degrees.

The DPRK apogee perigee altitude does not match the JSpoC data, which gives a clearly lower apogee perigee at 465 km. This could in theory be due to initial errors in the JSpOC tracking data (the first few orbit determinations are always less accurate). But the magnitude of the difference is such, that I doubt that.

Assuming that the numbers in the DPRK radio bulletin are not based on actual North-Korean tracking data, but instead based on a pre-launch desired orbit, then maybe this could indicate that the satellite did end up in a slightly lower orbit than intended.

We'll see if the difference keeps standing with more western tracking data added...

[update: Jonathan McDowell suggested that perhaps the Koreans used another spheroid (earth shape) to refer to. I doubt that: not only would I expect similar discrepancies in the apogee altitude as well in this case (the apogee altitudes given by JSpOC and N-Korea are close), but moreover, 30 km is a large difference. I know of no ellipsoid that differs by as much as 30 km from the WGS84 ellipsoid]

[update 2:  Bob Christy makes some very interesting remarks on his webpage, which also support the idea that orbit insertion did not go as intended].

North Korea has launched Kwangmyŏngsŏng 4

Launch of KMS-4 (still from N-Korean tv announcement)

My previous blogpost of Feb 4 (with an update on Feb 5) discussed the announced launch of a new North Korean satellite, Kwangmyŏngsŏng-4 (KMS-4), from Sohae satellite Launch center in the northwest of North Korea.

Yesterday (Feb 6), North Korea suddenly shifted the start of the launch window one day forward, from February 8 to February 7 (local date). No reason was given for this date shift.

The actual launch happened this morning at 00:29 UT (February 7, 2016), according to USSTRATCOM.

It appears to have been successful, to the extend that  they did successfully put an object into orbit, as the US military tracking network confirms. As the history with KMS 3-2 shows, whether the payload is really operational is another question and as for yet unanswered.

North Korean television announced the successful launch a few hours ago, in a bulletin in characteristic fashion, including images of the launch and of Kim Jong-Un watching the launch from Sohae:

Launch time

The launch time prediction of my previous post (and in this seesat list post) turns out to have been correct.

I indicated a launch between 00:24 and 00:41 UT (a 17 minute period out of a 5 hour window indicated by the North Koreans). The start of this window at 00:24 UT was based on the assumption of a launch at a similar solar elevation at Pyongyang as during the 2012 launch of KMS 3-2 (the end at 00:41 UT was based assuming a launch exactly 5 2 hours after Pyongyang sunrise rather than at a similar solar elevation to 2012).

The actual launch occurred at 00:29 UT, only a few minutes from the start of the window which I indicated. It corresponds to a solar elevation of 18.0 degrees at Pyongyang (the 2012 launch happened at a solar elevation of 17.5 degrees).


Orbit

The first orbital elements from JSpOC show two objects in orbit as a result of the launch: an A-object (catalogue number 41332, 2016-009A) and a B-object (catalogue number 41333, 2016-009B). The A-object is likely the satellite.

The A-object moves in  a 97.5 degree inclined, 465 x 502 km sun-synchronous polar orbit with an orbital period of 94.3 minutes. The satellite makes daily morning passes around ~9h am. It has a repeating ground-track every 4th day. This is consistent with a remote-sensing role.

The orbit is somewhat lower and  more circular than that of North Korea's previous satellite, KMS 3-2, which was initially placed in a 495 x 588 km orbit. Like the 2012 launch, North Korea had to perform a dogleg manoeuvre to attain an orbital inclination of 97.5 degrees after launching due south from Sohae (see discussion in my previous post).

The second, B object is the spent upper stage of the rocket, and is moving in a 433 x 502 km orbit.

The map below shows the satellite's ground-track during the first 5 orbits after launch:

North Korea's ruler Kim Jong-Un watched the launch from the grounds of the Sohae Satellite Launch Center. In the image below, he is observing the rocket ascend from a viewing platform which appears to be in front of the oval building that was erected at Sohae between March and July 2014 (see this satellite photo analysis on the 38 North blog).

A few more stills of the launch, taken from the North Korean tv broadcast:

The launch of Kwangmyŏngsŏng 4 is the second time that the North Korean rocket program was successful in placing an object in orbit. North Korea itself claims a number more successful launches, but these failed according to western sources as no objects were tracked in orbit.

Current spatial separation of the orbital planes of KMS 3-2 and KMS 4

Note added 18:00 UT, 7 Feb: a brief update noting inconsistencies between early western tracking data and a DPRK announcement is here.