13
Defining "retrieval" as "returning a commercial satellite to earth" then as of this moment there is no known capability to do that. (Ground-ruling out capsules like Dragon that return themselves with internal cargo).
As you mention Shuttle was designed for that but it was decades since it performed that function.
One could speculate about the X-37 and ...
10
The degree of orbital shadowing experienced by an orbiting object with small orbital altitude is determined by its beta angle (normally used in reference to LEO objects but the concept applies to lunar orbiters as well).
The angle is taken between the satellite's orbital plane and the vector to the Sun. Depending on the value of the beta angle, a satellite ...
7
There is no circular orbit that has a share of 50:50 between night and day.
The possible times are a bit less than 50% to 0% night or, respectively, a bit more than 50% day to 100% day.
The two extreme cases are:
an orbit that is aligned with the terminator (the border between night and day on the surface) is in perpetual daylight.
an orbit that passes ...
5
It all depends on how you define "dayside" and "nightside", and how you define "entering" or "exiting" either one of them for a satellite.
I suppose a big part of the confusion comes from this statement:
Being in a polar orbit, Chandrayaan-2 enters the dayside of the Moon crossing the north pole, traverses through the dayside and enters the nightside ...
4
It literally eats away at surfaces made of certain materials. It's pretty crazy. According to Space Mission Analysis and Design ("SMAD", 3e, by Wertz and Larson), Atomic oxygen (which I'll call ATOX thanks to user1209304's comment), is "the predominant atmospheric constituent" from 200 to 600km, and is a dominant force above 170km (around which it actually ...
3
Taken purerly in ideal terms, a satellite that has no additional forces acting on it will keep doing whatever it was previously doing rotation wise, but that may in fact be a carefully set slow rotation that keeps an antenna or camera facing earth for comunications or earth science, or fixed if it was a telescope watching a distant star. So either of your ...
3
Google Maps Moon likely uses a Simple Cylindrical projection for storing their map data. This is fine for the majority of the globe, but there are problems at the poles. Here are a few reasons why imagery of the poles is problematic:
The data is prone to discontinuities because it has the entire top or bottom edge of the rectangular projection converging on ...
2
The strong distortions and star-like stripes are an artifact of Googles' image processing. For comparison, here is a screenshot of our own South Pole :
I increased the contrast to make the artifacts more visible - the ice itself just has less contrast than the rocky features of the Moon.
2
The lighting is different at the poles. The sun is always very close to the horizon. There are some crater floors at the poles that never see sunlight. These crater floors are always inky black.
Likewise there are polar plateaus and mountain tops that enjoy nearly constant sunlight. Shadows cast across these plateaus are always long though. And these long ...
2
To expand on @gremlinWrangler's mention of
tidal effects
radiation pressure
YORP
let's not forget
Spacecraft Aerodynamic Torques NASA SP-8058, see also Passive Aerodynamic Stabilisation of Low Earth Orbit Satellite Bak, T. & Wisniewski, R., Spacecraft Guidance, Navigation and Control Systems, Proceedings of the 3rd ESA International Conference held ...
2
If i read your quote correctly, it doesn't state that a burn at the inertial y-axis is cheaper than a burn at the LON, but it explains that your satellite will encounter an acceleration towards north at +y and south at -y, so your LON will in fact line up with the y-axis after a while because of the inclination change due to this perturbation, so it's still ...
1
After the discussion here I finally switched to measuring the integrated density of the complete sat trail, subtracted background noise and compared the result against the known star HD 211599 (mag 8.87). Here I also subtracted the background noise. The Excel formula is attached.
For Starlink 29 I calculated a magnitude of 7.59 near the horizon.
Nice :-)...
1
The BBC News article Satellites to monitor whale strandings from space describes the use of the WordView-2 satellite to image mass standings of whales, and references the recent Open Access (non-paywalled) paper in PLOS ONE Using remote sensing to detect whale strandings in remote areas: The case of sei whales mass mortality in Chilean Patagonia which ...
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