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Quantum astronomy could create telescopes hundreds of kilometers wide

scientificamerican.com

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Re: Quantum astronomy could create telescopes hundreds of kilometers wide

#31

Post by HDMI_Cable »

Gravityloss wrote: post #24
qayxc wrote: post #21

Earlier quoted context omitted.

Launch costs are only a fraction of the total cost of orbital telescopes, so don't get your hopes up. For reference, the WFIRST telescope came with satellite bus and 2.4m mirror for free yet already has a 3.2 billion dollar price tag attached to it. Even the most expensive launch provider would be less than 10% of that cost. It only weighs about 4 metric tons by the way, so there's that. Just a quick reality check on…

I wonder, if you know you were launching one every six months for the next 20 years, what would the unit cost be? You might be able to use a commercial satellite bus for example. It would be fine if some would experience failures, as there would be the next one already lined up. Just put different instrument(s) at the end of the optical path in each. As example, Hubble has five instruments. https://hubblesite.org/mis…

Do we need that many telescopes though? It seems like one only needs many 5 at any given time.

Re: Quantum astronomy could create telescopes hundreds of kilometers wide

#32

Post by Gravityloss »

HDMI_Cable wrote: post #31
Gravityloss wrote: post #24

Earlier quoted context omitted.

I wonder, if you know you were launching one every six months for the next 20 years, what would the unit cost be? You might be able to use a commercial satellite bus for example. It would be fine if some would experience failures, as there would be the next one already lined up. Just put different instrument(s) at the end of the optical path in each. As example, Hubble has five instruments. https://hubblesite.org/mis…

Do we need that many telescopes though? It seems like one only needs many 5 at any given time.

One can already see that the existing terrestrial and space telescopes have long queues for observing time.

Maybe more experimental instruments would be nice as well.

Re: Quantum astronomy could create telescopes hundreds of kilometers wide

#33

Post by Jlz2021 »

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Re: Quantum astronomy could create telescopes hundreds of kilometers wide

#34

Post by gmkiv »

_Microft wrote: post #8
gmkiv wrote: post #2

I shudder to think of the difficulty in maintaining phase coherence at optical wavelengths for the baselines they mention in this article.

They want to store the state of received photons on „quantum harddrives“, transport them to the same place, read the states out and let them interfere locally. This is the mentioned paper from december 2020 about hour-long optical storage (by Chaun-Feng Li et al.): https://arxiv.org/abs/2012.14605 (Earlier article from 2015 about this storage technique: https://newatlas.com/quantum-encryption-storage-drive/35553/ )

The state (phase) of the received photon will depend on the position of the receiver. Even if you have a perfect quantum hard drive, you still need to maintain the position of your receivers to within a wavelength. That will be hard to do if they are separated by a long distance.

Re: Quantum astronomy could create telescopes hundreds of kilometers wide

#35

Post by rbanffy »

_Microft wrote: post #11
Cthulhu_ wrote: post #10

Earlier quoted context omitted.

Yeah that would be cool, the Hubble telescope has been massively successful but I would have thought there would be much more projects like that. The James Webb one will be next, but I feel like that one's really risky; they took years to develop and build it, and it's going out to a point of space where it's infeasible to send someone up there to fix it if there is a problem. A ring of radio telescopes in high orbit…

I like the ideas of "solar gravitational lensing telescopes" and "lunar crater radio telescopes". The former would place a telescope extremely far from the sun and use its gravitational lensing effect, the latter would turn a crater on the moon into a giant radio dish. Here is a link for the latter. https://www.nasa.gov/directorates/spacetech/niac/2020_Phase_...

The Moon could be good place for optical interference - on Earth you need to use fiber (or QHD's) to carry photons from one place to the other, but on the Moon you have a reasonable vacuum so you may be able to get a large base with only mirrors or line-of-sight communications.

Re: Quantum astronomy could create telescopes hundreds of kilometers wide

#36

Post by rbanffy »

I wonder what would it take to send a pair of optical telescopes on lunar landers (unmanned?) and attempt to do it using vacuum instead of optical fiber as a medium to join them.

A lot of the things that make it complicated on Earth just aren't there on the Moon. Plus, we have a great excuse to keep a couple astronomers and engineers around to service the telescopes.

Re: Quantum astronomy could create telescopes hundreds of kilometers wide

#37

Post by jjk166 »

HDMI_Cable wrote: post #31
Gravityloss wrote: post #24

Earlier quoted context omitted.

I wonder, if you know you were launching one every six months for the next 20 years, what would the unit cost be? You might be able to use a commercial satellite bus for example. It would be fine if some would experience failures, as there would be the next one already lined up. Just put different instrument(s) at the end of the optical path in each. As example, Hubble has five instruments. https://hubblesite.org/mis…

Do we need that many telescopes though? It seems like one only needs many 5 at any given time.

There are currently 35 space-based telescopes in active service with 6 planned to launch in the next 12 months.

[0] https://en.wikipedia.org/wiki/List_of_space_telescopes

Re: Quantum astronomy could create telescopes hundreds of kilometers wide

#38

Post by qayxc »

mrfusion wrote: post #27
qayxc wrote: post #21

Earlier quoted context omitted.

Launch costs are only a fraction of the total cost of orbital telescopes, so don't get your hopes up. For reference, the WFIRST telescope came with satellite bus and 2.4m mirror for free yet already has a 3.2 billion dollar price tag attached to it. Even the most expensive launch provider would be less than 10% of that cost. It only weighs about 4 metric tons by the way, so there's that. Just a quick reality check on…

But how much of that telescope cost is because of high launch costs. Ie using the lightest materials, overbuilding because maintenance is impossible, etc.

Hard to tell in detail, but not as much.

The primary cost factors are instrument development, ground segments, staff (over years, e.g. 5-10 years development plus ~5 years primary mission plus extensions), testing, and building (no economy of scale here).

The most counter-intuitive observations is that the cheaper your launch-costs, the higher the portion they represent w.r.t. total mission cost. A "cheap" (e.g. sub-50 million dollar) telescope for example would have launch costs come in at up to 50% of the total cost when launched on a medium-sized launcher or with a second payload.

It's a multivariable optimisation problem and the best solution depends on the variables that you want to optimise for.

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