Lecture 1 Flashcards

1
Q

How does a rocket work in vacuum?

A

It uses the action and reaction force of expanding gases.

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2
Q

Why do we observe from space? (The BIG factor)

A

Lack of atmosphere:
Possibility of achieving diffraction limited images
Possibility of observing across the electromagnetic spectrum with 100% transmission
Possibility of accessing information with no or almost no thermal background (in IR/μWave)
Long uninterrupted durations

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3
Q

What are some alternative concepts to observing from space? (Name at least two, not alternative techniques like rockets etc)

A

Very high altitude (if atmosphere becomes opaque at relevant wavelengths)

Adaptive optics, changing wavelength region (if extreme spatial resolution is needed)

Telescope networks (If long uninterrupted observation duration is needed)

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4
Q

Give an example where long uninterrupted observation time is needed.

A

Exoplanetary transit searches
Helioseismology
Micro-lensing

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5
Q

Major problems with network observations?

A

Weather
Rotation of the earth
Network uniformity

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6
Q

What are some concrete alternatives to observing from space?

A

Airplanes
Balloons
(Sounding rockets)

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7
Q

Name one pro and one con of using airplanes as a space observing alternative.

A

Advantages: Repeatability, change of instruments, different topics, multiple flights, large telescope, man-operated, cost

Disadvantages: max altitude 15km, no high-energy observations, expensive to operate, safety restrictions, cost

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8
Q

Name one pro and one con of using balloons as a space observing alternative.

A

Advantages: Cost, complexity, re-flyable, Components are cheaper (simpler) and can be changed, flights of tens or even hundreds of days duration possible.

Disadvantages: Not higher than ~ 40km

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9
Q

Name one pro and one con of using sounding rockets as a space observing alternative.

A

Advantages: Access to true space, Less expensive than satellite, Retrievable (recycle payload)

Disadvantages: Short flight duration (5-10 minutes), Components must be space qualified (expensive), Small payloads

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