Updating the changing tumble period of the USA 144 decoy

click diagram to enlarge

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.

Keyholes, IGS 1B and the USA 144 decoy

Yesterday evening it was clear again. I obtained data on two of the three Keyhole KH-12's, USA 129 (96-072A) and USA 186 (05-042A); on the defunct Japanese SAR IGS 1B (03-009B); and used the EF 100/2.8 Macro USM to capture the enigmatic HEO object USA 144 debris/decoy (99-028C).

The latter object is an interesting one. It was part of the launch of what is believed to be the second stealth reconnaissance satellite, Misty-2. After being picked up by amateur observers and observed for some time, doubts began to grow whether it really was the main payload. Ted Molczan determined from the obital evolution that the object did not appear dense enough to be an operational satellite (i.e. USA 144 itself), something further suggested by the fact that it appeared to be slowly tumbling. Instead, it is either a weird piece of debris from the Delta IV used to launch USA 144; or a deliberate decoy used to get attention away from the real payload. See here, here and here for the details.

Below are one of the images of the USA 144 Decoy which I obtained yesterday evening (it is crossing the northwest corner of Pegasus here), it's orbit, and the launch patch of the 1999 launch.

Click images to enlarge

The object was almost 10 seconds early relative to a 17-day old elset. It shows a slow but clear brightness variation over the image series.

The KH-12 Keyhole USA 186 (05-042A) was 2 seconds early relative to an elset of the previous day. USA 129 (96-072A) was on-time. IGS 1B (03-009B) was 0.25s late.

The Misty 2 decoy, USA 129, IGS 1B and more

Yesterday evening was a very clear evening. A bright moon lit the sky though.

Several objects were imaged. Two Keyhole satellites were captured: USA 129 (96-072A) and USA 161 (01-044A). For the first time this year, the Japanese IGS 1B (03-009B) defunct radar satellite was in range again, always a sure sign spring has arrived. Below are two images, of USA 129 and IGS 1B.

(click images to enlarge)

Among the HEO objects, the SIGINT USA 200 (08-010A) and the USA 144 deb/Misty 2 decoy (99-028C) were captured.

The latter is an interesting object. Launched in May 1999, a bright object from the launch was tracked by amateur observers (see story here). After some time it became clear from the orbital behaviour of the object, that it could not be a real operational payload. Rather, it is a piece of debris or a decoy meant to draw attention away from the real stealth payload. The object is bright, but probably small and very lightweight, and moving in a 2700 x 3100 km orbit. Below is the image I obtained on a pass of this object last evening.

(click image to enlarge)