# Tag Info

37

There are a couple of reasons. The distance from the L2 to Earth is only 1.5 million km away. The L4/L5 are 1 AU, or about 150 million km away. That leads to a reduction in link margin of 40 db, or 1/10000. That is quite significant. In order to compensate for that difference, you either need a bigger radio dish, more power, or a loss in data. As you ...

31

Space telescopes like Spitzer, Herschel, Planck, WISE, and in few years Webb, need to observe in the mid and far infrared wavelengths. The infrared radiation of normal spacecraft temperatures, even if kept cold by our standards, would look like a bright light at those wavelengths. (Google black-body radiation to learn more.) The infrared detectors need to ...

26

As stated, the answer to the question has to be yes, a telescope on the Moon can have significant advantages over a telescope on Earth, because of Earth's atmosphere. That's why we have space telescopes. However that is the wrong question. The real question is what advantages, as well as disadvantages, does a telescope on the Moon have over a telescope ...

23

I'm afraid it would be extremely difficult - simply the number of photons reflected off a planet surface and reaching Earth (and the telescope lens, however big) within timeframe for a solid photo is too small to create any meaningful image. Planets are not stationary; they orbit their stars, and that means long-exposure photo will show them as a trails. Of ...

23

There are two parts to this question. One is around speed (or apparent angular velocity) and one is around size. The Moon's apparent velocity is small, so it is easy to set up a telescope or camera to take a photograph at an appropriate exposure. Many satellites, and the ISS are much closer, so the apparent velocity from the observer's perspective is a ...

23

As several nations' governments and plenty of amateurs pointed radio frequency antennas at the sites and received signals, one might conclude that they were observed. Observation does not have to imply visible light observation. See this http://www.arrl.org/eavesdropping-on-apollo-11 My recollection from the time is that plenty of amateurs tuned in to the ...

22

Short answer No it hasn't been possible to see what was happening on the Moon, from Earth. The angular size of an object like the Lunar Module is much much smaller than the best angular resolution available in 1969. To imagine what happens when the resolution of the telescope is not sufficient, let's observe a strip of black and white lines with ...

21

No they were not. Telescopes, even today cannot resolve that small a detail from the distance. LCROSS, orbiting the moon was able to barely resolve the lunar modules left behind. More good details in this similar question and answer on the Astronomy site: Visibility of the Apollo-11 Module

20

It's not currently possible to get the details of a planet from a distance like a light year or more. Furthermore the projects mentioned below do not aim to get good images of the surface, but only to detect exoplanets, and do basic measurements. The reason is that getting detailed pictures of the surface is beyond current technology capability and research. ...

18

After looking through various mission articles on Wikipedia, the Mars Reconnaissance Orbiter's HiRISE camera has an aperture of 19.7 inches (50 cm), which Wikipedia claims is "the largest so far of any deep space mission". This camera allows it to take extremely detailed pictures of the surface. If you're looking for other large-diameter telescopes which ...

15

From Earth, you can't. This is actually quite a common question, and was answered by Telescopes.com. To see the Lunar Rover, for instance, would require a 75m telescope, far larger than anything ever built! The shadow of the Lunar Decent Stage is a bit larger, but even that is quite difficult to achieve, requiring the perfect timing, although even then, it ...

14

This is already done, especially with radio telescopes. For example, we've had the Very Large Array for a couple of decades, and we now have LOFAR and the VLT. It certainly would be possible to have an array of telescopes spread across the globe, or even an array of satellite telescopes. LIGO (not for electromagnetic wave detection though) will eventually ...

14

Nitrogen is a relatively inert diatomic (N2) gas, but also importantly, while there are other gases that refuse to react with much anything even more so, like e.g. Helium, Nitrogen is cheap since it's often a byproduct of industrial processes. It is also frequently readily available at scientific facilities in its liquid form for being an extremely ...

14

No. Not too unprotected, as you put it. There are several misconceptions that I find common about the JWST, that need to be addressed: JWST primary mirror elements are not made of glass and do not shatter on impact It's primary hexagon mirror elements are made out of Beryllium powder pressed into blocks, that were later cut in half to create two mirror ...

12

"Resolved images of a geostationary satellite were obtained on October 30, 2009, with the adaptive optics on the largest telescope on the planet, the 10 m Keck-II on the 14000 foot summit of Mauna Kea." Here ya go: Reference

10

It was, in the sense that all spacecraft have relationship to each other. Okay, beyond that, let's see how they are related. Wikipedia talks about the design of Hubble: Once the Space Telescope project had been given the go-ahead, work on the program was divided among many institutions. Marshall Space Flight Center (MSFC) was given responsibility for ...

10

Voyager's Infrared Interferometer Spectrometer (IRIS) has an aperture of 0.5 m (19.685"). This is not an imaging instrument though (resolution=1 pixel). The large aperture was needed to provide enough sensitivity. If we take the question literally, Kepler would qualify with its heliocentric orbit at a distance of 1 AU. It has a 1.4 m primary mirror.

8

To answer your original question regarding the state of affairs of space telescopes, from the US (NASA), besides JWST, there are two large space telescope projects. Work has started on the WFIRST (wide field infrared survey telescope). The LUVOIR (large ultraviolet/optical/infrared survey) telescope is in the study phase. WFIRST was originally a dark ...

8

Compared to what we already have, for example the Chandra X-ray Observatory that already has the orbital path one third as long as the distance from the Earth to the Moon (apogee 133,000 km and perigee 16,000 km, or 83,000 and 9,900 miles respectively), I don't think there's enough incentive to put a similar observatory on the surface of the Moon. There are ...

8

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 bias, which allows them to be focused with good resolution onto a film surface using the magnetic field. "Electrographic cameras for the vacuum ultraviolet" by ...

7

Really simplified answer: Anyone can see the moon. It's huge. You normally can't see an artificial satellite, it's tiny. When you can see it, it's a tiny point, like a distant star. Same goes for a camera / telescope. What you call "High detail" of the moon is probably tens or hundreds of metres across per pixel on the moons surface. A satellite is just not ...

7

How do we have telescopes that are powerful enough to see nearby galaxies, such as Andromeda (M31), but are unable to see TRAPPIST-1 or the other exoplanets in its solar system in detail when TRAPPIST-1 is only 39 light years away? You don't need a telescope to see M31. It has an apparent magnitude of 3.4, which means it is easily visible to the naked eye, ...

7

Yes. According to the NASA paper "Hubble Space Telescope Pointing Control System Design Improvement Study Results", in the first full paragraph on page 2, the author states The nominal control algorithm is a standard proportional-integral-derivative (PID) operating at 40 Hz using the rate gyro assembly measurements. If you want more information on ...

7

The spectrum you show from Titan was taken using the IRIS spectrometer aboard Voyager 1. Of course Voyager 2 had one as well. A huge amount of work went into developing and optimizing the design in order to develop a precise optical instrument that would survive both the high g-force and vibrations of launch, and the years in a space environment while ...

6

Hubble and various others have proven this (although this was already proven from ground observatories) There are some excellent pictures of lensed objects online, such as this galaxy arc on Hubblesite - this one was found in 2011: That was lensed from another stellar object, but there should be no difference between the sun and other stars etc.

6

In general IR instrumentation can work at higher temperatures, just poorly, in comparison when cooled properly. Usually when designing an instrument with a known coolant lifespan it makes sense to ensure it can at least function (even if degraded in quality) after the coolant runs out. Space can be 'cold' if managed properly. IR instruments like REALLY ...

6

In space, the notion of temperature is not the same as on Earth: Temperature can only apply to matter which vacuum has not. Space is near vacuum, so its temperature is irrelevant to large and dense objects. Satellites (including telescopes) are made out of matter and therefor can heat or cool. They are full of electronics that produce heat, and receive ...

6

The Celestron telescope is not stationary. It can be moved around inside the space station to look through any window. It is however just used to observe the Earth, and the reason for that is the orbital velocity of the ISS. Moving at almost $8km/s$, the view change with an angular velocity of 3.88 arc-degrees per second because the station rotates to keep ...

6

Just for reference, here are the largest apertures (visible or almost visible) sent to every planet that I can find. Note that some of them are kind of difficult to quantify. (Sorry for the mixed units...) Mercury- 15 cm- Mariner 10 (Messenger's largest was a 12cm x 12cm square) Venus- 7 inch from Galileo, but if you don't count that, likely only a few ...

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