Voit lisätä twiitteihisi sijainnin, esimerkiksi kaupungin tai tarkemman paikan, verkosta ja kolmannen osapuolen sovellusten kautta. Halutessasi voit poistaa twiittisi sijaintihistorian myöhemmin. Lue lisää
1/12
A few days ago I tweeted about #Trident-II 5D #SLBM tests and their range. But how about apogees?
One informative test was that of 10 September 2013. This one was observed, by accident, and these observations learn us a lot. Here is a thread with an analysis.pic.twitter.com/CXcQAM9fiL
2/12
On 10 September 2013, German photographer @JanHattenbach was making a photographic time-lapse of the night sky at the island of La Palma, when something odd streaked through his view. Here is a time-lapse movie of the event, courtesy of Jan:https://vimeo.com/335978703
3/12
At the time, as Jan was wondering what he photographed exactly, I suggested that this might be a ballistic missile test. Which was shortly after confirmed, when the US Navy acknowledged a Trident-II 5D #SLBM test that night.
4/12 Here is a stack of the images and a detail of one of the images. The distinct "puffs" and trail brightenings visible in the movie and on the images are engine firings of what is likely the PBCS reorienting while deploying RV's during the post-boost phase.pic.twitter.com/NobXJlb244
5/12 At that time we managed to identify a Maritime Broadcast Warning for the RV target area in front of the African coast. It was while searching for more Trident test related Broadcast Warnings last week, that I bumped into another Broadcast Warning for this test, one (cont.)
6/12 (cont.) ...related to the launch hazard area and missile stage drop zones. Together these allowed to reconstruct the actual ground trajectory of the 10 Sept 2013 Trident-II D5 test, and a ballistic trajectory fitting these, with a range of approximately 9800 km:pic.twitter.com/DCYpTy36Jd
7/12
But there is more: the images by @JanHattenbach from La Palma can be used to gain further information about the #apogee altitude of the test!
8/12 From the ground track, we can calculate the theoretical sky track as seen from La Palma for ballistic trajectories for several apogee altitudes, and see which one fits best with the actual observations. I astrometrically measured all the images to get sky positions.
9/12 Turns out, the best fit of the observed positions to the theoretical sky tracks is for a ballistic trajectory with an apogee of approximately 1800 km (NB: note that the starmap depicts positions in RA and declination, not azimuth and altitude):pic.twitter.com/iRIEd6gJi2
10/12 So we can conclude that the Trident-II D5, on a 9800 km range ballistic trajectory, reaches an apogee altitude of 1800 km. Amazing how informative a chance photographic observation of a missile test can be!pic.twitter.com/1JaxowQ3dB
11/12 The apogee of 1800 km is somewhat higher than the 1200 km typically quoted. That might be due to this test not having been aimed for maximum range. This means the trajectory had to be "lofted' somewhat, if the same missile velocity as for maximum range is used.
12/12 With the same velocity impulse as the 10 Sept 2013 test, but less "lofted", I get a maximum range of ~10 300 km, and then the apogee reached is the 1200 km frequently quoted.
Twitter saattaa olla ruuhkautunut tai ongelma on muuten hetkellinen. Yritä uudelleen tai käy Twitterin tilasivulla saadaksesi lisätietoja.
