AST101 - Lecture 20 Space Probes

How does the atmosphere impact light?

• The atmosphere absorbs and scatters light

• Not all wavelengths of light can travel through the atmosphere

• The atmosphere is opaque at some wavelengths

• Half the light makes it to the surface and half of it cannot

• Infrared does not make it to the ground (absorbed in the atmosphere)

• Turbulence in the Earth’s atmosphere distorts images

• For long exposures and large telescopes (required for dim objects) this blurs the image

• Without corrective measures, resolution for ground based telescope is limited

What are the steps of transfer orbit?

1. Start in the inner orbit

2. Engine burn to speed it up

3. It is now in the transfer orbit

4. Do a 2nd burn to speed up

5. End in the outer orbit

   1. No fuel is used except at burns 2 and 4

   2. The rest of the time you are costing in the orbit

What are some obstacles that satelitte face in space?

Power and Communication

Components of Launch Vehicles?

• Contain 

  • Payload

  • Fuel 

  • Oxidizer

  • Pumps

  • Engine

How do they deal with the issue of power?

• Satellites powered by inner solar systems (solar panels) that convert sunlight into electricity

• Also have a outer solar system

  • Radioisotope thermoelectric generator. Uses radioactive plutonium to generate electricity

  • For satellites further than Saturn

• Can only do it until Jupiter (and still need huge solar panels)

  • Farther you go sun has less effect

How do they the deal with the issue of communication?

• Spacecraft communicate with Earth using radio

• Large dishes are used to focus the very weak signals

• Data rates tend to be very low

• Light travel time makes for long delays

  • It is a few minutes to mars

  • Round trip delay is 13:45 to New Horizons to send back its images