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98 votes

Does it make any scientific sense that a comet coming to crush Earth would appear "sideways" from a telescope and on the sky (from Earth)?

The comet's tail always points away from the Sun. Yes, even when the comet is heading back into the outer solar system. This is because the tail isn't a 'trail' of where the comet has been, like a ...
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66 votes

Is pinging the Moon with a laser as shown on "The Big Bang Theory" possible?

There is a very nice Myth Busters video about bouncing a laser off the Moon linked below. To answer your question, current work is done with an array of corner cube reflectors on the Moon roughly 50 ...
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  • 148k
37 votes

Is there any way that real stars would move like they do in the classic Windows 3.x screensaver if traveling through space at extreme speed?

I do disagree with the other answers, not on the result, but on the reason. You don't need to go faster than the speed of light to pass through multiple stars in a few seconds. Putting aside the ...
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  • 471
36 votes

Is pinging the Moon with a laser as shown on "The Big Bang Theory" possible?

The University of Texas's McDonald Observatory performs laser measurements of the distance to the Moon using retroreflectors left by the Apollo astronauts. You can read all about it in the McDonald ...
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15 votes

Does it make any scientific sense that a comet coming to crush Earth would appear "sideways" from a telescope and on the sky (from Earth)?

While those movies probably do it because that's how comets are commonly depicted, it might not be that inaccurate. Remember that the Earth itself is moving around the Sun, so if a comet is heading ...
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  • 1,075
15 votes

Does it make any scientific sense that a comet coming to crush Earth would appear "sideways" from a telescope and on the sky (from Earth)?

If you're the comet, the way to hit Earth is not to head directly for it. That's because Earth is orbiting the sun: you need to aim at where Earth will be, not where it is right now. For example: By ...
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14 votes
Accepted

First LED left on another planet⁺ by humans?

July 20, 1976, Mars, Viking 1 lander. In the article "Viking gas chromatograph–mass spectrometer" by Rushneck et al, Review of Scientific Instruments 49:817-834 (1978), section G (pp. 828-9) ...
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12 votes
Accepted

Why is there no microscope on the Mars 2020 rover?

The MAHLI camera of Curiosity may focus from infinity down to only 18.3 mm working distance. At minimal distance the resolution is 13.9 µm per pixel. It may image objects of some tens of meters in ...
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10 votes

Accumulated environmental damage to Hubble main mirror

From here: http://www.spacetelescope.org/about/faq/ How do you protect and clean the lens of the Hubble Space Telescope? Hubble doesn’t have a lens. Like all large telescopes, Hubble uses a ...
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9 votes

Was Hubble really related to spy satellites?

This answer addresses the headline question, rather than the detailed content that suggests a connection between HST and a KH9. There may be a connection between the Hubble and a KH11. Refer here ...
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8 votes

How fast do optical surfaces get dirty or damaged in space?

In addition to the space weathering phenomenon described by ebv, optical surfaces can and do get dirtied by other mechanisms as well. In particular, outgassing from the rest of the spacecraft and ...
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8 votes
Accepted

What is the "space grease" used to lubricate the ISS robotic arm? What are the material considerations for it?

The lubricant is a Braycote vacuum grease: Braycote 602-EF. There is good information on the Latching End Effector (LEE) lubrication task (the task that actually applies the grease to the Space ...
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8 votes

First LED left on another planet⁺ by humans?

The Vega 1 balloon that entered the atmosphere of Venus on June 11, 1985, had LEDs on the anemometer: The diameter of the rotating anemometer was 25 cm. The rotor was mounted on ball bearings, and ...
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8 votes
Accepted

JWST - pick-off mirrors?

A pick-off mirror is a mirror that takes light from the telescope's common optical path and directs the incoming light to a specific instrument or sensor. There are two use-cases for them (at least as ...
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7 votes

Data rate in optical free space communication systems

You need to look carefully at how it's measured. One of the major contributors to data rate is availability: with low Earth orbit satellites they might only have a few minutes of downlink opportunity ...
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5 votes
Accepted

What's the largest optical telescope mirror ever put in space?

The winner (as of 2019) would be the ESA Herschel Space Observatory with a focal mirror of 3.5M/11.5ft (Image Source) Optical could include infrared, visible and ultraviolet, but not microwaves. ...
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5 votes
Accepted

Determine envelopes for the payloads?

For STS payload induced enviroments, grab yourself a copy of the Space Shuttle User's Handbook and you will find plenty of data starting on page 31 of the pdf. Vibration, noise, thermal, pressure (...
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5 votes
Accepted

Why do the LAGEOS' satellites have four germanium corner cube reflectors out of over 400?

D.A. Arnold "Optical and Infrared Transfer Function of the Lageos Retroreflector Array", 1978, NGR 09-015-002 (P179) confirms that they're for infrared measurements, and adds some interesting info: ...
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  • 12.3k
5 votes

Have optical zoom systems been used in space exploration?

The video camera on the Apollo LRV had zoom, used in the well-known Apollo 17 liftoff footage.
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5 votes
Accepted

Why does Unity look transparent?

Much of the Unity spacecraft appears (almost) transparent in this image; you can see the blue sky right through it. This is absolute nonsense; you cannot see the sky through Unity's airframe. It is ...
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5 votes

There are only a few suppliers of optical terminals: what is the reason?

Challenges Mass production and industrialization: The industry has geared up over decades to supply radio equipment such as phased-array antennas and hardware on satellites. Shifting the production ...
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4 votes
Accepted

How does the thin gold film in the glass of spacesuit helmets block thermal IR but transmit visible? What's the property?

@BlakeWalsh started to figure out the answer here and finished here but declined the invitation to post the answer, so I'll finish by posting it by proxy. Why is gold "gold-colored"? Several answers ...
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  • 148k
4 votes

How does the thin gold film in the glass of spacesuit helmets block thermal IR but transmit visible? What's the property?

If I Recall Correctly, The gold (and silver) was an early version of dichroic optical filters. Thin films of gold and silver, when applied in a specific order, create "thin-film interference" which ...
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  • 189
4 votes
Accepted

How would 2 JWSTs make stereo pictures?

Let's think about what stereo pictures give us scientifically rather than aesthetically. It's information about depth. How far something is away. Why scientifically? Because while bass players and ...
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  • 148k
4 votes

Have optical zoom systems been used in space exploration?

The Closed Circuit TV (CCTV) cameras in the Space Shuttle Payload bay had optical zoom lenses. Zoom capability magnifies or reduces the size of objects in a camera's field of view by adjusting ...
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4 votes
Accepted

How does the camera make the exhaust of the Electron's RP-1/LOX exhaust transparent?

In this image of a Falcon 9 takeoff (CRS-14), you can see some transparency in the exhaust of the (much larger) Merlin 1D: I can make out the rear half of the engine bells through the exhaust (this ...
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  • 121k
4 votes

Was Hubble really related to spy satellites?

Reading Wikipedia's KH-11 Kennen I found this ... "KH-11s are believed to resemble the Hubble Space Telescope in size and shape, as the satellites were shipped in similar containers. Their ...
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4 votes

Is there any way that real stars would move like they do in the classic Windows 3.x screensaver if traveling through space at extreme speed?

It helps to suppose that you're flying your ship somewhere closer to a galactic nucleus than we are. Sure, the nearest star to us (after the Sun) is several light years away, but if you get within a ...
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  • 888
4 votes

First LED left on another planet⁺ by humans?

July 20, 1976, Mars, Viking 1 lander. (You're really not going to like this one.) The lander's cameras included an array of 12 photodiodes to measure various things. One reference even plots each ...
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