bit of administrationbit of administration …. • lab 2 – new observation dates: march 22 -...

Bit of Administration ….Bit of Administration ….•• Lab 2Lab 2

–– New observation dates: March 22 New observation dates: March 22 -- April 5April 5•• No need to duplicate observations in hand!No need to duplicate observations in hand!

–– New due date: April 9 at my officeNew due date: April 9 at my office

•• HomeworkHomework

•• ReadingReading–– BSNV pp. 153 BSNV pp. 153 -- 168168

•• No office hours today No office hours today –– Feel free to eFeel free to e--mail for later in weekmail for later in week

AstronauticsAstronautics

•• Interplanetary TravelInterplanetary Travel

•• The Central Concept …The Central Concept …

The paths of interplanetary spacecraft areThe paths of interplanetary spacecraft aresimply orbits around the Sun …simply orbits around the Sun …

And the spacecraft obey the same physical lawsAnd the spacecraft obey the same physical lawsas do planets.as do planets.


•• Transfer Orbit = Minimum Launch EnergyTransfer Orbit = Minimum Launch Energy

•• Launch in the direction of motion of the launch platform.Launch in the direction of motion of the launch platform.

•• Arrive at destination at aphelion ( for outer target) or Arrive at destination at aphelion ( for outer target) or perihelion (for inner target) of spacecraft orbit.perihelion (for inner target) of spacecraft orbit.

(Aphelion (Aphelion -- point of orbit most distant from Sunpoint of orbit most distant from SunPerihelion Perihelion -- point of orbit closest to Sun)point of orbit closest to Sun)

Transfer Orbit for the MoonTransfer Orbit for the Moon


•• Transfer Orbit = Minimum Launch EnergyTransfer Orbit = Minimum Launch Energy

•• Launch in the direction of motion of the launch platform.Launch in the direction of motion of the launch platform.

•• Arrive at destination at aphelion ( for outer target) or Arrive at destination at aphelion ( for outer target) or perihelion (for inner target) of spacecraft orbit.perihelion (for inner target) of spacecraft orbit.

(Aphelion (Aphelion -- point of orbit most distant from Sunpoint of orbit most distant from SunPerihelion Perihelion -- point of orbit closest to Sun)point of orbit closest to Sun)

••Advantages Advantages -- Fuel efficiencyFuel efficiency

••Disadvantages Disadvantages -- Long travel timeLong travel time


•• Gravity BoostsGravity Boosts

•• Gain in energy due to gravitational “slingshot” aroundGain in energy due to gravitational “slingshot” arounda more massive body.a more massive body.

•• Note: More massive body loses energy, but in case of Note: More massive body loses energy, but in case of planet and spacecraft this is not a problem!planet and spacecraft this is not a problem!

AstronauticsAstronautics•• Gravity BoostsGravity Boosts

In frame of JupiterIn frame of Jupiter but Jupiter is moving …but Jupiter is moving …

In frame of Solar SystemIn frame of Solar System

AstronauticsAstronautics•• Gravity Boosts Gravity Boosts -- NASA missionsNASA missions

The Physics of LightThe Physics of Light•• Light as a Wave = Light as a Wave = Electromagnetic RadiationElectromagnetic Radiation

•• Wavelength (Wavelength (λλ) has units of length) has units of length•• Frequency (Frequency (νν) ) -- number of crests passing per secondnumber of crests passing per second

-- has units of cycles per second, or Hertzhas units of cycles per second, or Hertz•• Speed Speed -- for light, for light, c = 3x10c = 3x1055 km/seckm/sec

Wavelength

3 x 105 km/sec


•• Wavelength (Wavelength (λλ) has units of length) has units of length•• Frequency (Frequency (νν) ) -- number of crests per secondnumber of crests per second•• Speed Speed -- for light, for light, c = 3x10c = 3x1055 km/seckm/sec

Small wavelengthSmall wavelengthLarge frequencyLarge frequency

Large wavelengthLarge wavelengthSmall frequencySmall frequency


•• Wavelength (Wavelength (λλ) has units of length) has units of length•• Frequency (Frequency (νν) ) -- number of crests passing per secondnumber of crests passing per second

-- has units of cycles per second, or Hertzhas units of cycles per second, or Hertz•• Speed Speed -- for light, for light, c = 3x10c = 3x1055 km/seckm/sec

ν =cλ

The Physics of LightThe Physics of Light•• Electromagnetic Electromagnetic

SpectrumSpectrum

1 km = 1000 m1 km = 1000 m1 m1 m1 mm = 0.001 m = 101 mm = 0.001 m = 10--33 mm1 1 µµm = 10m = 10--66 m (“micron”)m (“micron”)1 nm = 101 nm = 10--99 m (nanometer)m (nanometer)

The Physics of LightThe Physics of Light•• Electromagnetic RadiationElectromagnetic Radiation

•• Light acts as an electric forceLight acts as an electric force

•• Light acts as a magnetic forceLight acts as a magnetic force

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NS

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The Physics of LightThe Physics of Light•• Electromagnetic RadiationElectromagnetic Radiation

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AntennaAntenna

The Physics of LightThe Physics of Light•• Doppler ShiftDoppler Shift

The Physics of LightThe Physics of Light

•• Doppler ShiftDoppler Shift

•• Source moving toward observer orSource moving toward observer orobserver moving toward light source observer moving toward light source

Shorter WavelengthShorter WavelengthHigher FrequencyHigher Frequency

BlueshiftBlueshift

•• Light source moving away from observer orLight source moving away from observer orobserver moving away from light sourceobserver moving away from light source

Longer WavelengthLonger WavelengthLower FrequencyLower Frequency

RedshiftRedshift



•• Source across observer’s line of sight Source across observer’s line of sight

Same Wavelength as emittedSame Wavelength as emittedSame Frequency as emittedSame Frequency as emitted

No ShiftNo Shift



∆λλrest

=vc

v = velocity of light source or observer (+ => toward each othv = velocity of light source or observer (+ => toward each other)er)λλ = rest wavelength= rest wavelength∆λ∆λ = change (shift) in wavelength= change (shift) in wavelengthc c = 3 x 10= 3 x 1055 km/seckm/sec

bit of administrationbit of administration …. • lab 2 – new observation dates: march 22 -...

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