Images from ground-based telescopes are invariably distorted by the Ea

The conclusion is about a causal relation:

Space telescopes are better in one feature, and HENCE they will make earth telescopes obsolete.

Stating a negative feature of the space telescopes attacks this causal relation (though it may not directly attack the possibility that earth telescope will be obsoleted). Because space telescopes has a negative feature they will NOT be able to make the earth satellites obsolete.

If one considers "ground-based telescopes will soon become obsolete" the conclusion then your point is definitely valid. But if one considers "Superior feature of space telescope will cause ground-based telescopes to be obsolete", then option E is correct. In GMAT this causal relation as a conclusion is often tested.

For the same reason stated above option B is wrong. It does not attack the causal relation, but only supports why earth based telescopes may not be obsoleted. (Moreover, the condition that was used to prove that Space telescopes will replace earth telescopes, still holds good - even after mounting the telescopes on higher grounds, the distortion will not be eliminated, and hence the space telescopes still remain better of the two - nonetheless, this does not play any role in attacking the causal relation.)

Hey,

I have a question regarding choice E.
Stating that space telescopes are not adapted for certain purposes does not imply that ground-based telescopes are. There is no mention of the fact that ground-based telescope is able to capture more light.

Please help

saby1410, aritrar4, mk96, enigma1504 - Missed some tags to this question. Here is a detailed analysis. Hope you find it useful.

Images from ground-based telescopes are invariably distorted by the Earth's atmosphere (in some way, whether winds, dust etc)

Orbiting space telescopes (above Earth's atmosphere) should provide superbly detailed images. Note the use of "should" - presumably because Earth's atmosphere does not interfere in their working. Does it actually happen, we don't know.

Conclusion: Ground-based telescopes will soon become obsolete for advanced astronomical research purposes.

We need to weaken that ground based telescopes will become obsolete. They may have a disadvantage to space telescope but they may have some advantage too. Let's look at the options.

(A) An orbiting space telescope due to be launched this year is far behind schedule and over budget, whereas the largest ground-based telescope was both within budget and on schedule.

Irrelevant. There is no implication here that orbiting telescopes are far more expensive and difficult to launch. We are just told about this year's project is lagging while the project of ground telescope was on time and budget. We don't know what budget was allocated to each project.

(B) Ground-based telescopes located on mountain summits are not subject to the kinds of atmospheric distortion which, at low altitudes, make stars appear to twinkle.

So one kind of atmospheric distortion (which makes stars appear to twinkle) can be taken care of by placing the ground based telescopes on mountain summits. But does this take care of all atmospheric distortions? Does it make ground based telescopes relevant? We don't know. So will ground based telescopes become obsolete? Can't say.

(C) By careful choice of observatory location, it is possible for large-aperture telescopes to avoid most of the kind of wind turbulence that can distort image quality.

So another kind of issue can be taken care of by carefully choosing location. So again, does this mean ground based telescope will stay relevant? Cannot say.

(D) When large-aperture telescopes are located at high altitudes near the equator, they permit the best Earth-based observations of the center of the Milky Way Galaxy, a prime target of astronomical research.

How we get the best "Earth based observations" is irrelevant.

(E) Detailed spectral analyses, upon which astronomers rely for determining the chemical composition and evolutionary history of stars, require telescopes with more light-gathering capacity than space telescopes can provide.

A certain method which is used by astronomers to find data about stars requires telescope with more light gathering capacity than space telescopes. For at least this application then, ground telescopes will remain relevant. It is a method used by astronomers so it is reasonable to assume that ground based telescopes provide this facility. Else, how do the astronomers use detailed spectral analyses? After all, astronomers rely on it for determining the history of stars.
Hence it weakens that ground based telescopes will soon become obsolete for advanced astronomical research purposes.

Answer (E)

Note that either you can have ground based telescopes or space telescopes. There is nothing else possible. What is not on the ground is above ground (in space). One specific use for which telescopes are used today (astronomers rely on Detailed spectral analyses) needs more light gathering capacity than space telescopes. So ground based telescopes must be providing those.