82
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Why are so many space telescopes placed in LEO instead of at Lagrange Points? And why do we hear about Hubble more than any Langrange-orbit telescope?
The reason there are so few spacecraft placed at Lagrange points is that it's much harder to get there. Launching sizeable payloads to Earth escape velocities requires a very large vehicle and is ...
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47
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Is it safe to observe the ISS with the naked eye?
It's safe.
The ISS is about 100 meters across at its widest, and it's 400km away; this calculator tells me that makes an angular size of ~0.014 degrees. The sun's angular size is about 0.53 degrees....
- 170k
41
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Is it possible to observe space debris with Binoculars?
Yes, I've done it myself in my backyard in suburban Houston.
During a spacewalk in ISS increment 50, an MMOD shield intended for the axial port of Node 3 was lost. It's visible in this video ...
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29
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Could Hubble observe the night side of the Moon?
Hubble can in fact observe the Moon, and has done so. Here's a picture of the Apollo 17 site (The upper right is from Apollo 17 mission itself). The x shows where the actual site is. You can also see ...
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28
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Is it safe to observe the ISS with the naked eye?
No problem, even with a telescope
Not only is it perfectly safe with the naked eye, it's also not a problem at all with a large aperture telescope.
At first, I tried looking at the ISS with a 80-...
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18
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Why do satellites appear to move faster when overhead and slower closer to the horizon?
Here's a geometric construct to back up @uhoh's answer. Start with a satellite in orbit about earth (radius $R$) at height $h$.
The inner circle is the surface, outer is the orbit. Each blue wedge ...
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17
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Why are so many space telescopes placed in LEO instead of at Lagrange Points? And why do we hear about Hubble more than any Langrange-orbit telescope?
To add to the existing good answer about the practicalities of launching to Lagrange points, it's also worth considering why the missions which have gone that far are using the unstable Lagrange ...
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Is it safe to observe the ISS with the naked eye?
In addition to Russel's answer:
The ISS' albedo is far lower than 1, so the brightness is going to be less than 1/1400.
Those solar panels convert 30% of the sunlight into electricity, and ...
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When was the last time that Starman/Roadster was seen?
The latest measurements used by JPL Horizons to calculate its trajectory were reported on 3/27 as follows:
2018-Mar-27: Two reporting sites (J94 & K93) extend data arc one month.
That is the ...
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12
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Does the ISS have zenith-facing windows?
There are windows on Zvezda from which you can see zenith, but these aren't facing exactly zenith. It doesn't seem as though any other segment on the ISS have zenith windows.
From this website, at ...
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Why do satellites appear to move faster when overhead and slower closer to the horizon?
They are moving mostly toward or away from me at a near-zero angle of incidence (even at 20K Kilometers or 30K Miles overhead)?
Mostly this I believe. But your distance is off. It is very difficult ...
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11
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Why are so many space telescopes placed in LEO instead of at Lagrange Points? And why do we hear about Hubble more than any Langrange-orbit telescope?
The other thing is you need more power to transmit large amounts from the Lagrangian points so that requires bigger solar panels hence more mass.
Another reason Hubble is in LOO is that the ...
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Was the command/service module visible from the lunar surface?
I'll calculate the visibility of a diffuse 50% gray sphere with a 6 meter diameter. Averaging over all Sun-object-observer configurations that might be similar to a 4 x 11 meter shiny cylinder since ...
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11
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Are there any Earth observation-like spacecraft orbiting other planets or moons?
The category of "observation satellites" is broad, because there are many types of observation (different wavelengths that reveal different characteristics of the observed planet). Because you're ...
- 128k
10
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How does it look to be on the surface of Sedna?
Sedna at perihelion is 76 AU from the Sun, meaning it receives about 1/76^2 = 1/5776 as much light from the Sun as Earth does. This distance reduces the sun from a -26.7 apparent magnitude to a -17.3 ...
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Can we see the USA flag on the Moon from Earth?
I am not aware of an optical telescope capable of showing proof from earth. Part of the reason is the flags are pretty small and it's a very long distance. However, you can see the flags or what is ...
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When was the last time that Starman/Roadster was seen?
@uhoh's answers are correct in that we at LCO were the last to observe the Tesla Roadster. For some reason, a Distant Artificial Satellites Observation (DASO) circular was not issued in the March 2018 ...
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9
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How did Skylab's electrographic ultraviolet camera work?
Similarly to night vision devices, the light sensitive part is the photocathode, which releases electrons when hit by photons. The electrons at the photocathode are accelerated by the -25 kilovolt ...
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9
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Has an astronaut ever seen another object in LEO pass by that wasn't mission-related?
It turns out it might be very common for astronauts on the ISS (or previously the MIR) to spot satellites. This is the distribution of the number of satellites in LEO for different altitudes
As you ...
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8
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Is it safe to observe the ISS with the naked eye?
There's a lot of poor information out there regarding looking directly at the sun (or looking at it through a mirror). As a general rule-of-thumb, it's a bad idea to look directly at the sun, but that ...
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8
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Why do satellites appear to move faster when overhead and slower closer to the horizon?
tl;dr: looking at satellites between 300 and 1000 km altitude that happen to pass overhead, they definitely move the fastest when overead and slow way down. At the zenith they move 1.4 and 0.4 degrees ...
- 149k
8
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Why are so many space telescopes placed in LEO instead of at Lagrange Points? And why do we hear about Hubble more than any Langrange-orbit telescope?
In addition to the other reasons: a Lagrange point has advantages for some telescope types, but less so for others.
Earth is bright in visible light, IR and some radio wavelengths, less so in gamma ...
- 128k
8
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What is the fastest we could travel in space, or have ever traveled in space?
If you want speed, look for mass. Things closest to the Sun will tend to be moving the fastest.
For example the Messenger spacecraft reached almost 63 km/s when in an elliptical orbit who's ...
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7
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Have astronauts seen asteroids or comets?
And now meteoroid (i.e. burning asteoroid):
GIF:
(taken from ESA video)
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7
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Astrophotographer Thierry Legault is not convinced that DarkSat is darker than the others. Have photometric measurements been reported?
I was able to measure STARLINK 1130 (darksat, left) on March 19th, 2020, at Sternwarte Mirasteilas. Comparison object is STARLINK 1084 (same operational height, similar altitude above the horizon, ...
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7
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Will the Artemis Gateway Lunar Space Station be visible from Earth by amateur observers?
Gateway will almost certainly be observable by lucky and ambitious amateur astronomers.
The station's magnitude is more relevant than its size.
By comparison, JWST is physically smaller than Gateway ...
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7
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Will the Artemis Gateway Lunar Space Station be visible from Earth by amateur observers?
Will the Artemis Gateway Lunar Space Station be visible from Earth by amateur observers?
If they can see +15 magnitude stars routinely, they'll probably be able to see Gateway.
Answers to Good source ...
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6
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How was radio telescope observation data transferred before wide availability of high-speed Internet?
Transportation of data between observatories was done via magnetic tape using a standard or common format. At least this was the case for the Westerbork Synthesis Radio Telescope and the observatories ...
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6
votes
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Taking detailed photos of satellites using laser illumination
A common equation to express the best resolution of an optical system is based on the overlap of two Airy disks
$$ sin(\theta)\approx \theta \approx 1.22 \frac{\lambda}{D} $$
You can ask what size ...
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