Bit of Administration ….

2. Bit of Administration …. • Lab 2 • New observation dates: March 22 - April 5 • No need to duplicate observations in hand! • New due date: April 9 at my office • Homework • Reading • BSNV pp. 153 - 168 • No office hours today • Feel free to e-mail for later in week

3. Astronautics • Interplanetary Travel • The Central Concept … • The paths of interplanetary spacecraft are • simply orbits around the Sun … • And the spacecraft obey the same physical laws • as do planets.

4. Astronautics • Transfer Orbit = Minimum Launch Energy • Launch in the direction of motion of the launch platform. • Arrive at destination at aphelion ( for outer target) or • perihelion (for inner target) of spacecraft orbit. • (Aphelion - point of orbit most distant from Sun • Perihelion - point of orbit closest to Sun)

5. Transfer Orbit for the Moon

6. Astronautics • Transfer Orbit = Minimum Launch Energy • Launch in the direction of motion of the launch platform. • Arrive at destination at aphelion ( for outer target) or • perihelion (for inner target) of spacecraft orbit. • (Aphelion - point of orbit most distant from Sun • Perihelion - point of orbit closest to Sun) • Advantages - Fuel efficiency • Disadvantages - Long travel time

7. Astronautics • Gravity Boosts • Gain in energy due to gravitational “slingshot” around • a more massive body. • Note: More massive body loses energy, but in case of • planet and spacecraft this is not a problem!

8. Astronautics • Gravity Boosts but Jupiter is moving … In frame of Jupiter In frame of Solar System

9. Astronautics • Gravity Boosts - NASA missions

11. The Physics of Light • Light as a Wave = Electromagnetic Radiation • Wavelength (l) has units of length • Frequency (n) - number of crests passing per second • - has units of cycles per second, or Hertz • Speed - for light, c = 3x105 km/sec 3 x 105 km/sec Wavelength

12. The Physics of Light • Light as a Wave = Electromagnetic Radiation • Wavelength (l) has units of length • Frequency (n) - number of crests per second • Speed - for light, c = 3x105 km/sec Small wavelength Large frequency Large wavelength Small frequency

13. The Physics of Light • Light as a Wave = Electromagnetic Radiation • Wavelength (l) has units of length • Frequency (n) - number of crests passing per second • - has units of cycles per second, or Hertz • Speed - for light, c = 3x105 km/sec

14. The Physics of Light • Electromagnetic • Spectrum 1 km = 1000 m 1 m 1 mm = 0.001 m = 10-3 m 1 mm = 10-6 m (“micron”) 1 nm = 10-9 m (nanometer)

15. - - - - - - - - - - - - - - S S S S S S N N N N N N N N N N N N S S S S S S The Physics of Light • Electromagnetic Radiation • Light acts as an electric force • Light acts as a magnetic force

16. - - - - - - - - - The Physics of Light • Electromagnetic Radiation Antenna

17. The Physics of Light • Doppler Shift

18. The Physics of Light • Doppler Shift • Source moving toward observer or • observer moving toward light source Shorter Wavelength Higher Frequency Blueshift • Light source moving away from observer or • observer moving away from light source Longer Wavelength Lower Frequency Redshift

19. The Physics of Light • Doppler Shift • Source across observer’s line of sight Same Wavelength as emitted Same Frequency as emitted No Shift

20. The Physics of Light • Doppler Shift v = velocity of light source or observer (+ => toward each other) l = rest wavelength Dl = change (shift) in wavelength c = 3 x 105 km/sec