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78

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 simply impractical/impossible for many missions. For example, at the time of its launch, there was no launch vehicle in operation capable of lifting Hubble's 11000 ...


28

From here, discussing images of Mars taken by Hubble while near to its closest approach to Earth: The telescope snapped these pictures between April 27 and May 6, 1999, when Mars was 87 million kilometres from Earth. From this distance the telescope could see Martian features as small as 19 kilometres wide. Theoretically Our resolution is limited by the ...


26

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 more Hubble pictures of the Moon at this page.


23

The altitude difference is minor compared to the plane change. Even 23 degrees of plane change would require a prohibitively large change in velocity 2 * 7.5 km/s * sin(23 degrees / 2) = 3.0 km/s In reality the plane change required is greater than 23 degrees, because the two orbits don't have the same right ascension of ascending node. Hubble actually ...


23

It depends on whether you're talking about the original Hubble configuration or its current configuration. First, Hubble does not have any thrusters, so it does not have propellant to unload (thrusters could throw particles around the telescope, affecting its view. Read more here) Originally, the Hubble was designed to be returned via space shuttle, ...


20

No, Hubble is in low Earth orbit, much lower than the Moon. The shuttle delivered it to orbit, and the Shuttle can't get near the Moon. The image you reference is very similar to one that came from DSCOVR, which is at a point about a million miles from Earth between the Earth and Sun, which always sees the sunlit portion of the Earth. However, there are ...


17

There was a design requirement (PDF, page 30) for a "probability of no penetration" of 95% for 2 years. The Space Debris Handbook (PDF, page 137) indicates the main risk was considered to be a light leak in the aft shroud. I haven't been able to find any specifics on construction details that ensure this. Specifically, I haven't found any mention of ...


16

The aperture door is used to protect the telescope during launch and service operations, and to prevent the sun from shining down the telescope barrel. Here, the HST is being released from shuttle Discovery. The door opens soon after the HST has been released: The door closes automatically if the HST is pointed to within 20 degrees of the Sun's ...


16

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 points, when L4 and L5 are stable. It comes down to what happens if the satellite loses control. In unstable Lagrange points, if the satellite gets fried somehow ...


15

There is a docking ring on the JWST, so in theory astronauts could visit it. It would be easier to get to JWST than to the Moon, but more difficult than LEO like we have been doing. Edward Weiler, director of NASA Goddard Space Flight Center, had this to say on the subject: We cannot make the James Webb Space Telescope fully serviceable like the Hubble ...


14

From the HST Service mission 2 Media Guide (large PDF) The shroud and bulkhead support a gas purge system used to prevent contamination of the science instruments before launch. All vents used to expel gases are light-tight; that is, no stray light can enter the OTA focal plane. From this description, I suspect that the interior of the telescope was ...


14

This is the 1978 image of the Pluto system that led to the discovery of Charon. This is a negative, so the big black blob in the middle is Pluto and Charon. Charon? It's the little bump on the upper right of that blob. You can barely make out Charon. Additional satellites? No. This is a 1990 image of Pluto and Charon taken by the Hubble: This was before ...


12

The Hipparcos satellite was solely devoted to astrometry. It did not take 'regular' images, it used an eccentric Schmidt telescope to overlay images onto a grid. It finally resulted in a catalogue of stars, not an archive of images. It's purpose was to detect and find the position of stars in the sky. An 'image' taken by Hipparcos. As you can see, it's ...


12

The answer is a clear no because Hubble Space Telescope (HST) uses a fixed focal length of 57.6 m. The only thing you'd achieve by re-purposing it as a solar concentrator would be to melt its focal plane assembly and likely everything around it. HST is a Cassegrain reflector and its mirror assembly is utterly unsuitable to applications where adjustable focal ...


11

As @Vedant Chandra says, Hipparcos was dedicated to astrometry. To do this properly, you need to make sure your measurements are accurate. The pointing accuracy of your satellite is a nice specification, but a system that does not rely on this can achieve more accurate measurements. To do this, Hipparcos looks in two directions at once. The telescope ...


11

Supplementary answer: This answer covers most of the requirements well, but there is one incomplete statement: To do this would require only the folding of the solar arrays To fit horizontally in the payload bay and allow the Orbiter's payload bay doors to be closed, the telescope's aperture door must be closed and its high gain antennas also have to be ...


11

Yes. It is done by magnetic torquers. Magnetic torquer bars can provide control about the wheel-less axis, but they must also continue to dump momentum from the wheels to prevent wheel speed saturation. (emphasis mine) Source Source Another good reference on the attitude control system is here.


10

As of 2013, NASA still had a docking ring for the JWST. ① While they have no plans to service JWST, they left the docking capability just in case. The most likely service vehicles are either an Orion capsule (4 man) or Dragon 2 Capsule (7 man); a Dragon 2 atop a Falcon Heavy could easily reach and have delta-V sufficient for return. ② References ① Space....


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 ...


9

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 curved mirror to focus starlight. This mirror is located deep inside the telescope, protected by its long tube-like structure. As there is no atmosphere around ...


9

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 technology was essentially that of a spy satellite but pointing the other way! As they found out soon after Hubble was launched the satellite vibrated when the solar ...


8

None whatsoever. If JWST has issues, it is basically out of luck. Maybe one day, Orion might be able to go visit, but Orion is a lousy repair platform compared to the Shuttle. Shuttle had more crew (7 vs 4), more room for equipment, a place to dock the Hubble as a work platform, an RMS to move heavy equipment around (in and out of the Hubble).


8

Without arm and cargo bay and with only one EVA because the Orion has no airlock, the cabin can be refilled with air once, there would be some serious limitations. Orion could maybe be extended with an extra module for such a mission. Orion is not really a complete spaceship like the shuttle was, it is an exploration vehicle component which needs a larger ...


8

Some effects of the mirror imperfection could have been reverted, others not. Citing from a workshop on HST image restauration: "The fundamental loss of HST imaging science as a result from spherical aberration is not a loss of resolution; rather, it is a loss in the ability to detect faint objects, especially in crowded fields." On this workshop, ...


8

For the solar arrays, they have been replaced a couple times, and that "generation" of solar arrays always looked warped According to this quora post https://www.quora.com/Considering-Hubble-Telescope-is-25-years-old-have-the-solar-panels-been-replaced-at-least-once-given-their-degradation-in-space-happens-much-faster it was due to a failed compensation ...


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

Sure it could. There is also a possibility of Dream Chaser doing a service mission. Hubble is expected to remain in service and not reenter until at least 2028. That should give the BFR plenty of time to work. At that point in time, one could either bring it back or else perform a service mission to restore it to work. If there isn't anything done, then a ...


7

In a somewhat implicit way, Chapter 16 (By Joseph Tatarewicz) of NASA's SP-4219, "From Engineering to Big Science", provides an answer: While the $6 million per month seems like a lot for storage, the spacecraft had to be kept in a mammoth clean room with active air conditioning and filtering systems operating constantly, some nitrogen purging of areas ...


6

Those are the High Gain Antennas, and according to this systems overview, they are steerable: High Gain Antennas. Each HGA is a parabolic reflector (dish) mounted on a mast with a two- axis gimbal mechanism and electronics to rotate it 100 degrees in either direction (see Fig. 5-9). I believe they're mounted pointing in opposite directions (12 o'clock ...


6

For the first servicing mission, there's a nice weight breakdown in the spress kit. For later missions, that table isn't included. I've added weights of the major replacement units where possible, but the list remains incomplete. First servicing mission was STS-61. This is the list of items carried up/down by that mission. Not all of this was installed on ...


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