Lecture 1 Flashcards
How does a rocket work in vacuum?
It uses the action and reaction force of expanding gases.
Why do we observe from space? (The BIG factor)
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
What are some alternative concepts to observing from space? (Name at least two, not alternative techniques like rockets etc)
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)
Give an example where long uninterrupted observation time is needed.
Exoplanetary transit searches
Helioseismology
Micro-lensing
Major problems with network observations?
Weather
Rotation of the earth
Network uniformity
What are some concrete alternatives to observing from space?
Airplanes
Balloons
(Sounding rockets)
Name one pro and one con of using airplanes as a space observing alternative.
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
Name one pro and one con of using balloons as a space observing alternative.
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
Name one pro and one con of using sounding rockets as a space observing alternative.
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
