Why can't we just using existing space telescopes for planetary science?

[Glaran K'erman]

This may be extremely ignorant of me, and if it is I apologize in advance, but why couldn't we just point the various deep space telescopes at other bodies in our solar system. Only possible reason I could think of may be some sort of focal issue but aside from that it seems quite reasonable right?

[Kryten]

That does happen to some extent (e.g. the Hubble observations of Pluto which discovered the small moons), but there's very little relative time dedicated to it because they're built and funded as astrophysics missions. There have been and are proposals for dedicated planetary science space telescopes, but so far none have survived selection against more direct probes.

[MinimumSky5]

Also, taking Pluto as an example, the best Hubble images can just barely resolve a disk, while New Horizons has returned immensely beautiful images of its surface at a very high resolution. Also, Hubble cost $1.75 billion in 1980 to construct, and that doesn't take into account ground equipment, the launch or servicing missions. New Horizons cost $700 million in 2007 for construction, launch, support and public outreach, making it much cheaper.

[Bill Phil]

Also, taking Pluto as an example, the best Hubble images can just barely resolve a disk, while New Horizons has returned immensely beautiful images of its surface at a very high resolution. Also, Hubble cost $1.75 billion in 1980 to construct, and that doesn't take into account ground equipment, the launch or servicing missions. New Horizons cost $700 million in 2007 for construction, launch, support and public outreach, making it much cheaper.

Yes, but Hubble has done more than New Horizons. Beautiful images of deep space objects. More than just Pluto. Many objects.

[UmbralRaptor]

Space telescopes *are* used for planetary science (Kryten mentioned Pluto, but HST has also been used on Uranus, Neptune, and lots of asteroids and KBOs), but being able to get close does wonders for image resolution. Plus there are instruments/measurements (eg: particle detectors, magnetometers, mass spectrometers, laser altimeters) that make sense for craft doing close flybys or orbits but not ones that stay at earth.

[MinimumSky5]

I'm not saying Hubble is poor value for money, just that if you're looking at one specific object, a probe makes more scientific and monetary sense than a telescope.

[MoeKitsune]

Why does Hubble have amazing images of deep space objects, yet Pluto and Ceres look crappy from it's images of them?

[Shpaget]

I'm not saying Hubble is poor value for money, just that if you're looking at one specific object, a probe makes more scientific and monetary sense than a telescope.

But you're not using a telescope for one specific object.

New Horizons had only a few hours to take pictures of Pluto at their highest resolution, and a few weeks at the resolution higher than what we've had until then. HST has been taking pictures for more than 25 years, and will hopefully operate for some time.

Imagine if we haven't had space telescopes when it was discovered that the Shoemaker - Levy was about to hit the Jupiter. There would have been no time to launch a probe to take nice pictures. Since there were telescopes around, we just pointed them and took as many pictures as we pleased.

Yes, probes are awesome and they provide some otherwise unobtainable data, but a telescope is a much more versatile instrument.

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Why does Hubble have amazing images of deep space objects, yet Pluto and Ceres look crappy from it's images of them?

Because Pluto is tiny, while DSOs are absolutely huge.

[How2FoldSoup]

Why does Hubble have amazing images of deep space objects, yet Pluto and Ceres look crappy from it's images of them?

The simple answer is exposure times and relative sizes. Those beautiful nebulaes you see are dozens, sometimes thousands, of light years across. The simple difference in sizes between these two objects are many many orders of magnitudes. There is also much more light being emitting or reflecting off of these massive structures compared to pluto allowing your camera to absorb more photons and detail.

[SuperFastJellyfish]

Since we're speaking of relative sizes of bodies, I'll just leave this here as this is my favorite flash doohickey.

[Shpaget]

And speaking of apparent sizes and angular diameter, Pluto is about 0,09'', while Helix nebula is 22' (22' x 60 = 1320'').

So, Helix nebula has about 15 000 times larger apparent diameter.

[Camacha]

The simple answer is that they are different tools with different qualities and weak points. Hubble is flexible, yes has very distinct limitations in what it can resolve. Even the relatively nearby Pluto system is nothing more than a couple of pixels. A probe is much more specific, but is able to show us beautiful and detailed images of a few bodies.

They complement each other.

[windows_x_seven]

Pluto, by the Hubble Telescope:

Pluto, by New Horizons:

[Xannari Ferrows]

If there is ever a plan to launch a large binocular telescope into space, I would give anything to see a picture from that.

[Motokid600]

I just hope after Hubble falls back to Earth and after the JWST we get another visible spectrum telescope like HST.

[Camacha]

If there is ever a plan to launch a large binocular telescope into space, I would give anything to see a picture from that.

What would be the benefit of that? Over such long distances, images pretty much flatten. The third dimension pretty much disappears. Even when using binoculars to look at far-ish Earth bound objects, depth tends to disappear.

[Xannari Ferrows]

What would be the benefit of that? Over such long distances, images pretty much flatten. The third dimension pretty much disappears. Even when using binoculars to look at far-ish Earth bound objects, depth tends to disappear.

It would be able to decipher details of up to 1.454441043 • 10^-10 radians.

[colmo]

It's also more cost effective to build ground telescopes for viewing in the visible spectrum. They're bigger, and adaptive optics make the atmospheric perturbations disappear. Space telecopes, like JWST, specialise in the IR and UV, which the atmosphere absorbs strongly.

[PB666]

Yes, but Hubble has done more than New Horizons. Beautiful images of deep space objects. More than just Pluto. Many objects.

That wasn't the point really, hubble over its many lives has witnesses many things, but its not specifically designed to characterize small bodies that are only visible with reflected light.

But we need many more and better hubble like scopes. The webb scope is barely hobbling along out there, its past its mission life and has control issues.

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It's also more cost effective to build ground telescopes for viewing in the visible spectrum. They're bigger, and adaptive optics make the atmospheric perturbations disappear. Space telecopes, like JWST, specialise in the IR and UV, which the atmosphere absorbs strongly.

1. Space telescopes are not limited by their latitude or longditue, they can pretty much cover one hemisphere of the sky on any 'night'.

2. They a not limited by water dropplets in th upper atmospere, glare created by other light sources. Can pretty much fix on an object and remain so indefinitely.

3. You dont need to send people to nose bleed elevations in some foriegn country where politics and funding issues become an international problem.

4. You could move your scope potentially to a deep systm orbit and get better images, if you can get the power problem down.

5. one can, in a single point operation and a combined scope see gamma, xray, UV, IR, visible, microwave and ionized particles (cosmic rays). So for instance, if one suspects a star is about to nova, then point and start sampling.

[colmo]

1. Space telescopes are not limited by their latitude or longditue, they can pretty much cover one hemisphere of the sky on any 'night'.

2. They a not limited by water dropplets in th upper atmospere, glare created by other light sources. Can pretty much fix on an object and remain so indefinitely.

3. You dont need to send people to nose bleed elevations in some foriegn country where politics and funding issues become an international problem.

4. You could move your scope potentially to a deep systm orbit and get better images, if you can get the power problem down.

5. one can, in a single point operation and a combined scope see gamma, xray, UV, IR, visible, microwave and ionized particles (cosmic rays). So for instance, if one suspects a star is about to nova, then point and start sampling.

Bear in mind we're going to have 30m and 40m mirror ground scopes soon, v JWST's 6.5m - that's 20 times+ the equivalent light gathering capability. If making observations of a time sensitive nature e.g. exoplanet transits, that matters.

JWST cost iirc $8 billion. The EELT has been costed at €1.3 billion. We could build several huge ground scopes, giving greater coverage, for one space telescope, and they're serviceable, so likely will last longer.

The big scopes like EELT and TMT are in Hawaii and Chile, quite stable places. The worse trouble they've had was that issue in Hawaii with the locals being agitated, fearing the mountain god would be angry, but Chile is fine, and has a load of infrastructure already in place.

I did say visible light. Well aware of the value of e.g. HST observing in the UV to complement ground surveys.

I very much hope to get time on some of these toys in my planned future career (astrobiology), they all have their place.

[Glaran K'erman]

I have been learned! Thanks guys makes sense now why we're doing what we're doing now!

[Camacha]

It would be able to decipher details of up to 1.454441043 • 10^-10 radians.

Sorry, what?

[Robotengineer]

Sorry, what?

Angular resolution.

[WinkAllKerb'']

It would be able to decipher details of up to 1.454441043 • 10^-10 radians.

nice ; )

[tater]

Yep, resolution is a function of aperture (1.22Lambda/D), or the distance between 2 apertures (interferometry, which is mostly, but not only done with radio at the moment).