Wednesday 12 April 2023

Optically observing the RNLAF's 6U cubesats BRIK-II, HUYGENS and BIRKELAND


WATEC 902H2 Supreme camera with Samyang 2.0/135 mm lens and GPS time inserter

The Royal Netherlands Air Force (RNLAF) launched its first satellite, the cubesat BRIK-II (2021-058F), two years ago as part of the Virgin Orbit Tubular Bells rideshare on 30 June 2021 (see an earlier post here).

Two more satellites, HUYGENS (2023-001CN) and BIRKELAND (2023-001G) were recently launched for the RNLAF as part of the SpaceX Transporter 6 rideshare on 3 January 2023. These two satellites, which move in the same orbital plane, are co-owned by the RNLAF and the Norwegian Ministry of Defense.

The satellites are 6U cubesats, with the bus measuring 10 x 20 x 30 cm (roughly the size of a shoebox). Huygens and Birkeland have unfolding solar panels expanding their size to about 30 x 60 cm.


Brik-II during assembly and testing (image: Netherlands Ministry of Defense)


Rendering of Huygens (image: Nanoavionics)


orbits of the Brik-II, Huyugens and Birkeland cubesats


Over the past two weeks I have imaged all three satellites from Leiden - in the case of  Huygens and Birkeland even on multiple nights - using my WATEC 902H2 Supreme camera fitted with a 2.0/135 mm light telelens. 

Brik-II remained very faint during the one pass I imaged, but Huygens and Birkeland were surprisingly easy to see, as can be seen in the framestacks and video's further down in this blogpost.



Below are a framestack and a short video of the March 30 Brik-II detection. I have processed the video for visibility (which also increased the noise) as the cubesat was very faint: look for a very faint, fast object coming from the upper left corner.

I had tried to image the satellite earlier on several occasions the past two years, but this was the first time I had a positive detection.


Brik-II, framestack from footage taken March 30, 2023

video footage of Brik-II (very faint!)



Below are framestacks and video footage of passes of Huygens and Birkeland taken on March 30, April 4 and April 8, 2023. These two cubesats were much more readily visible than BRIK-II and you'll have no problem seeing them in the footage

The video footage of Huygens is from April 4, of Birkeland from April 8. They were (on all three nights involved) clearly better visible than Brik-II was on March 30. This is partly due to a better observing geometry, but it does seem that Huygens and Birkeland are really intrinsically brighter than Brik-II. They reached magnitude +7.5 to +8.

First, imagery - framestacks and brief video footage - of Huygens (2023-001CN) obtained on 30 March and 4 April, 2023:

Huygens on March 30,2023 (framestack)

Huygens on April 4, 2023 (framestack)

 video footage of Huygens on April 4, 2023


Next, imagery - a framestack, and a longer video - of Birkeland (2023-001G) obtained on 8 April 2023. The bright object initially seen passing in the upper left corner is a Starlink satellite (Starlink-5226): Birkeland is the fainter object coming from bottom right:

Birkeland on April 8, 2023 (frame stack)


 video footage (longer video) of Birkeland on 8 April 2023



All the imagery was captured with a WATEC 902H2 Supreme low-light-level cctv camera fitted with a Samyang 2.0/135 mm lens, filming at 25 frames per second. Accurate timing of the video frames was provided with a BlackBoxCamera GPSBOXSPRITE-2 GPS time-inserter.

The system delivers an astrometric accuracy of about 15 arcseconds. The FOV is about 2.7 x 2.0 degrees. The footage was shot from my home in the center of Leiden, the Netherlands (52.154 N, 4.491 E).

The image below shows the equipment in question. The box at left is the GPS time inserter. The PAL video feed from the WATEC camera goes from the camera into the time inserter, which imprints each individual videoframe with a millisecond-accuracy time derived from GPS signals. After passing through the time inserter the video feed is going to a digitization dongle, and is next recorded on a laptop.

WATEC 902H2 Supreme camera with Samyang 2.0/135 mm lens and GPS time inserter


I used my observations to provide these orbit updates for Huygens and Birkeland:

1 55093U 23001C   23098.81960162 0.00006982  00000-0  37378-3 0    02
2 55093  97.4857 159.4790 0014652 237.3630 122.6188 15.14989127    06

rms 0.004 deg   arc 30.85 Mar - 8.83 Apr UTC

1 55015U 23001G   23098.83187223 0.00009789  00000-0  53865-3 0    04
2 55015  97.4960 159.3843 0009401 256.5788 103.4395 15.14067850    03

rms 0.003 deg   arc 4.88 - 8.84 Apr UTC


These observations have wet my appetite to try to image more cubesats. The observations also underline (as we recently did in a conference publication as well) the power of relatively small but sensitive equipment. You really don't need a big telescope to track cubesats.

More on these satellites

With Brik-II, Huygens and Birkeland, the RNLAF is now entering active operations in the Space Domain.

Huygens and Birkeland are named after two iconic scientists, the Dutch Christiaan Huygens (1629-1695) and the Norwegian Kristian Birkeland (1867-1917). They were developed as part of the joint Milspace-2 program of the Dutch and Norwegian Ministries of Defense.

The two satellites operate as a pair, in the same 97.5 degree inclined orbital plane, Huygens currently in a 531 x 511 km orbit, Birkeland currently in a 530 x 517 km orbit. 

Their primary mission is ELINT: the geolocation and fingerprinting of Radar emissions. The two satellites are also used for experiments with formation flying.

Huygens and Birkeland orbit

Brik-II is named after Brik, the very first aircraft of a forerunner of the RNLAF, the "Luchtvaartafdeling" of the Royal Dutch Army, back in 1913. 

In Dutch, the word "brik" has several meanings: it is Dutch for "brick", as well as a slang name for a means of transportation (a cart or a car), in the latter case usually with the added connotation of it being somewhat decrepit.

The satellite is in a 60.7 degree inclined, 515 x 466 km orbit. Its experimental mission includes ELINT, communications, and Spaceweather monitoring. It was built for the Dutch Ministry of Defense by ISISpace in Delft. It is operated by the Defense Space Security Center in Breda.


"Brik", the first aircraft of the Dutch military, in 1913 (image Dutch Ministry of Defense)

Brik-II orbit 


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