All of these tracks were taken with the University of Arizona Steward Observatory Pomenis Astrograph at Mt. Lemmon. Pomenis is a 180 mm Takahashi Astrograph with a Apogee Alta F9000- 12um, 3056x3056 pixels camera. Credit goes to my team, graduate student Harry Krantz (the system engineering lead) and image processing and computer operations by Adam Block. Adam also does spectacular astrophotography with Pomenis which has been in the press lately.
While it's pretty amazing to track an object that size at 330,000 km with a 180 mm (7") telescope, there are a few things going for us: (1) Chandrayaan-2 (the lander stacked on top of the orbiter) is pretty large and covered with mostly gold MLI, (2) although its "cislunar", the angular distance from the moon (the "lunar elongation") is very large, until it enters lunar orbit, and (3) the solar illumination angle is very favorable. You can see the geocentric and selenocentric orbits in the animations on Wikipedia.
While it's pretty amazing to track an object that size at 330,000 km with a 180 mm (7") telescope, there are a few things going for us: (1) Chandrayaan-2 (the lander stacked on top of the orbiter) is pretty large and covered with mostly gold MLI, (2) although its "cislunar", the angular distance from the moon (the "lunar elongation") is very large, until it enters lunar orbit, and (3) the solar illumination angle is very favorable. You can see the geocentric and selenocentric orbits in the animations on Wikipedia.
The Indian Space Research Organization (ISRO) Chandrayaan-2 spacecraft inbound on its last complete geocentric orbit before lunar orbit insertion on 8/12/2019.
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8/15/2019, range about 255,000 km. Outbound on its last geocentric orbit towards lunar orbit insertion. 120 s integration time over about 1 h of tracking.
Satellite phase angle: 45 deg Lunar elongation: 176 deg Moon phase: 99.9 % |
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8/16/2019, range about 325,000 km. Here it is much closer to the Moon than us on its journey there. At this distance this 3x6 meter object appears quite faint. 360 s integration times over about 1h 18m of tracking.
Satellite phase angle: 48 deg Lunar elongation: 170 deg Moon phase: 99.2 % |
8/17/2019, range about 375,000 km. This was our last capture... it is likely we can detect it yet a little farther still. Complicating matters include the fact that the satellite is nearer to the moon in the sky (and the bright sky makes the spacecraft detection more difficult).
Satellite phase angle: 50 deg Lunar elongation: 160 deg Moon phase: 96.8 % |