# Tag Info

54

3753 Cruinthe ranks as target number 16832 in JPL's list of near earth asteroids that might be worth visiting, someday. With 16381 better targets, that "someday" most likely will be a long time from now, if ever. The problems with getting to Cruinthe are twofold. One issue is that its orbit is rather eccentric (0.51485). Changing an orbit's shape is an ...

16

Our Moon makes this possible. An asteroid with a low $V_\infty$ with respect to Earth making a close flyby of the Moon in the right direction could get into a distant orbit around the Earth. That object would likely continue to encounter the Moon, and could be ejected again. It is important to realize that things cannot just drift into orbit without ...

13

The challenge here is getting the pusher plate into position. The potential impactor is not generally traveling on an orbit that can be reached with low DV. So the only way with current(ish) technology to get 100-1000 tons of pusher plate alongside and stationary to an asteroid is if it uses an Orion drive. And if you have a fully working Orion then you can ...

13

Short answer is that you are confusing two different names: S509356 and 509356s. The 509356 in the JPL Small Body Database used by HORIZONS is not the same body as the S509356 you mention. Searching the JPL database (https://ssd.jpl.nasa.gov/sbdb.cgi) gives us details on 509356, a main-belt asteroid discovered in 2006. 509356 is a permanent designation ...

10

Not really. If an asteroid that was a loose collection of rubble was spinning, it would fall apart. The question is, how do you get it spinning? And would it do any good anyways? To make it spin one would have to apply an asymmetric thrust. The problem is, most likely if you can do this, then it will actually end up only affecting the area you are thrusting,...

10

Dangerous asteroids are those that can hit the Earth, and are large enough to cause substantial damage. There are currently no such known asteroids. (2020-02-21) There are two ways an asteroid could end up as considered dangerous: We discover it. There may be an asteroid bound for Earth at this moment, we just haven't seen it yet. This is fairly straight ...

8

Aerobraking would not work. If the asteroid shaved off enough speed to put it into orbit, the orbit would be highly eccentric resulting in repeated encounters with the atmosphere and eventual impact.

7

The NEA Scout contains multiple items aimed at controlling attitude: An inertial measurement unit that contains rate gyros that sense the vehicle's rotation rate with respect to inertial, A star tracker that senses the vehicle's orientation with respect to inertial, A set of large reaction wheels for coarse attitude control, A set of smaller reaction wheels ...

6

There is a paper on this subject that you can read here. Basically by fitting the data to a pure gravity simulation, there was some residuals, but when fitting it to the model $A_1r^2$, they could find a solution that seems to fit quite well. In this case, $r$ is the distance from the sun, measured in AU. The $A_1$ value that best fit is \$5.01\cdot 10^{-6} \...

6

OSIRIS-REx is packed all full of good stuff. I'll throw together a quick list of the scanning ones you're interested in. Also of note is that the entire spacecraft will be making that scanning motion shown in the gif, so as the asteroid rotates, all of these instruments will be able to have full coverage of it. OSIRIS-REx Visible and Infrared Spectrometer ...

6

All the data from the NEAR Shoemaker mission is archived at the Small Body Node of the NASA Planetary Data System. Asteroid surface properties (the regolith) is normally measured using images or spectra in the mid/thermal-infrared to determine the thermal inertia. This can vary considerably depending on whether the surface is made from coarse boulders to ...

5

It's a Bayesian thing. If one spots a low albedo asteroid, the odds are good that it's a carbonaceous chondrite asteroid that formed beyond the frost line and hence contains minerals that have become hydrated. Most of the observed low albedo asteroids are carbonaceous chondrites, and most of carbonaceous chondrite meteorites that have fallen to Earth have ...

5

There are no scenarios for either of those asteroids hitting the earth on the next approach. Both have been tracked carefully for years, and the closest approach has been calculated at 0.035428 Astronomical units, or 3.2 million miles (5.3 million km), which is 13 times as far away as the moon orbits the earth. That is close astronomically, but it is a very ...

5

The scenario is presented by the 2019 Planetary Defense Conference.

5

This depends on the size and composition of the asteroid. Many asteroids are loose rubble piles, held together by weak gravity only. So you can't really park a small ship on the surface and start thrusting: you'd end up pushing the ship through the asteroid. When the ship diameter is about the same as the asteroid, it could work.

5

Not touching upon how "useful" this could be as a stepping stone, as that's difficult to answer, but the more narrow question "Will a pile of rocks stick together at EML4, or drift apart due to tidal forces?" is quite answerable. An object near EML4 is acted upon by several forces, mostly the Earth's gravity balancing inertia in the rotating frame of ...

5

Yes it would work. But no, it would not work very well at all. If you are going to have the supremely powerful laser array available, you would be better off beaming the asteroid directly. The momentum transferred by boiling off a thin layer of the surface of the asteroid is many magnitudes more effective than using the same laser to accelerate lightsails. ...

4

You can certainly reverse a gravity assist to lose velocity. Most inner system probes do so. For a classic gravity assist the object has to leave the influence of the assisting body so for capturing an asteroid the answer is technically no, there is no way to achieve a low altitude circular orbit of a single body purely by gravity assists. It is certainly ...

4

The threat from comets gets a lot less attention for several reasons: the threat from comets is about 1% of that from asteroids (executive summary of the 2017 Report of the Near-Earth Object Science Definition Team, page 8), the warning time is often much shorter than for asteroids, mitigation of a threat from a long period comet is much harder for a lot ...

4

As reported on the Minor Planets Mailing List, 2012 TC4 was recovered by the European Southern Observatory's Very Large Telescope in Chile. Here's their reported astrometry data. According to the ESO's announcement, the observation at apparent magnitude 27 is the faintest near-earth asteroid so far measured. In the above stack of (37) 50-second exposures, ...

4

It looks like the tweet is screenshot of JPL's NEO close approach table (found here). JPL has definitions of many terms here.The 'nominal' miss distance is based off the latest/greatest prediction of the asteroid's trajectory, and the 'minimum' is the minimum of all the 3-sigma possibilities for it's range at close approach. This is the 3-sigma error ...

4

The list doesn't specify a distance to the Earth (the "ground") because this is always changing as the asteroid travels around its orbit. You can get an idea of the asteroid's orbit using the JPL Small Body Browser and typing the name into the search box. (The first entry (2018 AV2) won't work as it has been removed as likely to be part of the Apollo 10 ...

3

Practically speaking, the CW (Clohessy-Wiltshire) equations https://en.wikipedia.org/wiki/Clohessy-Wiltshire_equations are only useful for a first analytic look at understanding what is happening (they assume 2-body dynamics). For real world trajectory design these problems are solved using numeric targeting methods with full force model fidelity including ...

3

Capture inherently requires three bodies. By far the easiest way is with the moon being the third body. There is another capture scenario, though--take two asteroids that are orbiting each other. They approach very slowly, when they pass Earth they are moving just over escape velocity. They pass very close, the one moving forward at that point hits the ...

3

JPL has a nice data base Here's a screen shot: Notice some of the options. You can sort by minimum possible distance. For time range you can choose All available. They measure their distances in LD (Lunar Distance) or AU (Astronomical Unit). To get kilometers, multiply their LD number by 384,400 or their AU number by 150,000,000. They also give Vinf. ...

3

I haven't done an exhaustive search, but 433 Eros gets a lot closer and is larger (34.4×11.2×11.2 km). There's a long list of Mars-crossers with 18 candidates that may be larger than Phobos. It doesn't identify which 18 though. In this list of NEOs, 1036 Ganymed is the largest with a diameter of 32-34 km. Good luck tracing all their orbits and deciding ...

3

1:1 resonance means that each year the asteroid will be in approximately the same place as viewed from Earth as it was the previous year. This as compared to Pluto, which is in a 3:2 resonance with Neptune, meaning for every 3 Neptune years, Pluto will make 2 years. These should be a result of gravitational interaction between the two bodies. And yes, ...

3

There's the usual collection of overly dramatic news reports about this branch of NASA finding and tracking near-misses: express.co.uk reports a tracked object that came within 0.03860 AU. It's not clear when NASA first detected it. USAToday for a simulation drill that was run in mid-2019, as a tabletop exercise Monday-Friday at the 2019 ...

2

For years, wide field infrared orbital telescopes have been touted as the best way to complete a survey of NEO objects and give a greater warning time on potential close approaches. Astronsapper's Plantetary Society article talks about this partially. For years, proposals have been put forth to build these orbiting telescopes, but there is not a strong ...

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