SOLUTION
Passage Analysis

Images from ground-based telescopes are invariably distorted by the Earth's atmosphere.
• Telescopes based on land provide images that are distorted by the air around the earth.
Orbiting space telescopes, however, operating above Earth's atmosphere, should provide superbly detailed images.
• Telescopes in space orbit the earth and work above the atmosphere. Therefore, they should give detailed images not distorted by the atmosphere.
Therefore, ground-based telescopes will soon become obsolete for advanced astronomical research purposes.
• Thus, ground-based telescopes will stop being used for advanced research in astronomy.

Question stem Analysis
Which of the following statements, if true, would cast the most doubt on the conclusion drawn above?
This is a weaken question stem. We should cast doubt on the conclusion that ground-based telescopes will become obsolete for advanced astronomical research.

Prethinking

Weaken framework
What new information can decrease one’s belief in the conclusion that that ground-based telescopes will become obsolete for advanced astronomical research, given that space telescope images are not distorted by the atmosphere and can give superbly detailed images?

Weakener 1- Ground-based telescopes have some advantages that space-based telescopes do not have which is relevant for advanced research.
Weakener 2- Space telescopes have some significant disadvantage that makes them not suitable for advanced research, despite the lack of atmospheric distortion

Option Analysis

(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.
This statement points out only specific incidents and does not give any indication on why ground-based telescopes will not be obsolete. If space telescopes are more affordable then they should be at an advantage according to this option. Hence this is an incorrect answer.

(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.
This option says ground-based telescopes can evade atmospheric distortion of the type that leads to the twinkling of stars when placed on mountain summits. But we still do not know if all the atmospheric distortions can be avoided, we still do not know if placing these on summits will provide the superbly detailed images needed. Hence this option cannot weaken the claim as well.

(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.
Wind turbulence may not be the only factor that affects the image quality inside the atmosphere. Hence even if that is avoided, we cannot say the output will be at par with space telescopes. Hence this option is also incorrect.

(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.
This option specifies a particular location for a particular observation from the earth. But we need to compare ground telescope observations with space telescope observations to be relevant in this context. The absolute best earth-based observation may still be poorer than space-based observation. Hence this answer is incorrect.

(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.
Option E, in line with our weakener 2, provides a situation that is a disadvantage of space telescopes for the purpose of astronomical research.

The correct answer is E.