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Cees Bassa Profile picture
Cees Bassa
@cgbassa
Astronomer at @ASTRON_NL, working with the @LOFAR low frequency radio telescope. Tweets mainly about space related topics.
3 subscribers
Jan 7, 2022 • 11 tweets • 7 min read
During 2021, my #allsky camera took an photo of the sky from the Netherlands every 15 seconds. This image combines the 2.1 million images into a year-long keogram, showing the length of the night change during the year, the motion of the Sun and Moon, and lots and lots of clouds. In a keogram the pixels along the local meridian, the line along the sky from South to North, are plotted against time, as shown in this video. Keograms were developed for the study of Northern Lights, see blog.aurorasaurus.org/?p=1229 for more information.
Jan 16, 2020 • 7 tweets • 5 min read
This evening I got my first view of #DarkSat, the @SpaceX #Starlink satellite with a special coating to make it less bright in the night sky. The combined image below shows that #DarkSat is not much fainter than some of the other #Starlink satellites... What is going on here? 1/n This image shows the maximum pixel value of 18 individual exposures of 10 seconds each, taken at 1 minute intervals. Each individual image exposure contains a #Starlink satellite; they just happened to be separated in time by roughly a minute. Predicted positions are overlaid.
Sep 6, 2019 • 12 tweets • 18 min read
Tonight we're using the Dwingeloo @radiotelescoop to track the landing of the @isro #Chandrayaan2Live Vikram lander on the surface of the Moon. The lander just reappeared from behind the Moon and locked on to the Madrid telescope of the @dsn_status network. @radiotelescoop @isro @dsn_status @PI9CAM @tammojan The #Chandrayaan2Live Doppler curve has just reached its maximum. This means it has just passed over the lunar North pole and is now moving South towards the landing site.
Aug 30, 2019 • 15 tweets • 8 min read
It's not often that I retweet the US president, but he tweeted this image of the Iranian Safir launch failure. The image is very interesting as evidence suggests that it was taken by a US spy satellite on August 29th, 2019. Here's my analysis. The image shows the aftermath of an accident with an Iranian Safir rocket at the El Khomeini Spaceport. From the features of the launch pad, I find that the viewing directions of the camera match that of USA 224, a classified spy satellite.
May 26, 2019 • 8 tweets • 6 min read
This is the impact of a ~1600 satellite @SpaceX #Starlink constellation for a location at latitude 52 degrees. At any time, about 84 satellites would be above the horizon. During twilight and the entire summer, up to 15 of those visible (sunlit and above 30 degree altitude). These plots assume 53 degree inclined orbits at 550 km altitude, with 24 evenly spaced orbital planes, each having 66 #Starlink satellites. The total constellation would have 1584 objects. This is the initial @SpaceX plan for #Starlink.