Space Telescope in Pluto's orbit

[davidjeba]

Wondering, why cant we have a Hubble like telescope in Pluto's orbit looking at earth exploring our own solar system?
cant we detect NEO, asteroids etc and learn more about our solar system?

let JWT look beyond and hubble look within our solar system?


i just want to know why and why not...
just being curious...

[Hobbes-22]

Practical problems:
- it takes forever to get there
- data rate from Pluto is tiny: JWST downloads at 3.5 Mbyte/s, a spacecraft at Pluto will be closer to 1 kbyte/s
- observations get worse at long distance. It's much easier to detect small NEOs from Earth orbit than from Pluto's orbit
- the Sun gets in the way

[Don2]

Wondering, why cant we have a Hubble like telescope in Pluto's orbit looking at earth exploring our own solar system?
cant we detect NEO, asteroids etc and learn more about our solar system?

When taking pictures, you usually want to think about where the light is coming from. Often it is a good idea to have the light behind you. From Pluto, you would be looking at the dark side of planets on the same side of the sun as you. Also, large space telescopes are not pointed anywhere near the sun to avoid damage to the optics. Typically they are pointed at least 60 degrees away from the sun, and often more. Inner solar system objects could not be observed from Pluto because they would be too close to the sun.

A telescope at the orbit of Venus was considered for near Earth object searches. When looking away from the sun it would see the sunlit sides of Earth and of near earth objects. However it is difficult to transmit lots of data across the vast distances of interplanetary space, so the near earth object hunting telescope will be going to the Lagrange point called L1 (Google that if you don't know what it is). There is already a small telescope there called DSCOVR, and you can see pictures from it at the link below.

https://www.nesdis.noaa.gov/current-satellite-missions/currently-flying/dscovr-deep-space-climate-observatory

[launchwatcher]

Wondering, why cant we have a Hubble like telescope in Pluto's orbit looking at earth exploring our own solar system?
cant we detect NEO, asteroids etc and learn more about our solar system?

As others have suggested, Pluto's orbit is the wrong place to look for NEO's.   You want to be inside the earth's orbit, looking out, so you see the sun-lit side of the objects you're looking for against the dark and cold background of space.

There was a proposal (which was cancelled due to insufficient funding) to put an asteroid-hunting telescope in solar orbit at about the distance of Venus from the Sun: https://en.wikipedia.org/wiki/Sentinel_Space_Telescope

[Jim]

Wondering, why cant we have a Hubble like telescope in Pluto's orbit looking at earth exploring our own solar system?
cant we detect NEO, asteroids etc and learn more about our solar system?

let JWT look beyond and hubble look within our solar system?


i just want to know why and why not...
just being curious...

Hubble does look within the solar system.

[jbenton]

Another problem is electrical power supply.
The Hubble generates 2,800 watts of electricity. The smaller Kepler space telescope generated 1100 watts. These missions could benefit from the ample solar energy available at Earth's orbit around the Sun.

Making solar power work at Pluto's orbit, however, is a technical non-starter - so that leaves us with RTGs. A "radioisotope thermoelectric generator" - often described as a "nuclear battery" - uses the heat from radioactive decay of a material to produce electricity. Currently the substance that NASA currently uses is the Plutonium isotope Plutonium-238 (by the way, Pu-238 doesn't produce gamma radiation, so shielding doesn't involve a sever mass penalty).

The MMRTG - the RTG that Curiosity and Perseverance use - generates 125 watts when new, which degrades to 100 watts after 14 years. To power a Hubble-class observatory would require at least 28 of them if you want more than a decade of science (and 23 if you're fine with a short mission).

That's a problem. Each MMRTG costs over $100 million - so you'd need $3 billion for power generation alone. That's without even considering the subsystems required to actually use that electricity to make the telescope work. The Nancy Grace Roman Telescope - which has a primary mirror the same size as Hubble's - is going to cost NASA well over $3 billion. Hubble itself, with more instruments than Roman, cost even more than that, adjusted for inflation.

For more about RTG costs, see this:
https://www.osti.gov/biblio/1364515

On top of this, NASA only has a limited supply of Pu-238. At current production rates, it would take decades to produce enough plutonium for this one mission

The alternative to RTGs are nuclear reactors. A nuclear reactor in space is a political non-starter for the foreseeable future. On the technical side of things, however NASA recently developed a reactor for the "Kilopower" project which can generate 1000 watts. So I've read, (and this could be wrong) this cost only $20 million. However, RTGs are more reliable than reactors, as they have no moving parts. Further there are probably other problems with using reactors that I don't know about (I think heat rejection is a concern, not to mention the fact that the reactors produce gamma radiation).

EDIT: The topic of plutonium production recently came up in the ESA - Voyage 2050 thread. This post from that thread mentions some issues regarding Pu-238 production that I didn't consider, so I'll quote part of it here:

There is a possibility of increasing US Pu-238 production, but that's not the only thing that has to be increased. There are other limits along the supply chain, particularly how many fuel clads can be produced per year. Just increasing Pu-238 supply would mean that it would pile up, like pumping a lot of oil out of the ground but not having capacity at the refinery to process it.

[libra]

If you want a space telescope looking at the universe from the depths of the solar system, then THIS seems to be a better place than Pluto orbit.

https://en.wikipedia.org/wiki/Solar_gravitational_lens

Of course, it is even farther away and with all the caveats mentionned upthread. At least the loooooong trip is to a worthwhile place.

[arachnitect]

After the Pluto flyby they advertised time on LORRI as part of the extended mission. I don't know if anyone found a use for it besides looking at other KBOs.

[edzieba]

It's been proposed, but is unlikely:
https://twitter.com/AlanStern/status/969242036669829120

No fuel. No money.

[Greg Hullender]

Another reason to want a telescope at (say) 40 or 50 AU from the sun would be to get better parallax measurements.

[jbenton]

After the Pluto flyby they advertised time on LORRI as part of the extended mission. I don't know if anyone found a use for it besides looking at other KBOs.

It's been proposed, but is unlikely:
[Dr. Stern on Twitter]:

No fuel. No money.

Another reason to want a telescope at (say) 40 or 50 AU from the sun would be to get better parallax measurements.

It's been done, but I'm not sure how large the scientific return was: