1. Today’s APODAPOD  Read NASA website:  solarsystem.nasa.gov solarsystem.nasa.gov  IN-CLASS QUIZ THIS FRIDAY!!  Solar Lab, Kirkwood, Rooftop this week The Sun Today A100 Solar System Spacecraft

2. Events this week  AFTER CLASS – SOLAR LAB  2:30-3:30  TONIGHT - Kirkwood Obs  8:30-10:30 PM  TOMORROW – Thursday – Rooftop  8:30 PM Swain West WEATHER PERMITTING

3. What Does a Spacecraft Have to Do?  Propulsion  Navigation  Guidance  Power  Communications  (Launch)  (Solve problems autonomously)  (Life support) AND…. the spacecraft must function without maintenance for years, and be ultra -light- weight!

4. Spacecraft Propulsion  Propulsion: a means to change the speed of a satellite or spacecraft  Small corrections needed to stay in orbit  “Orbital station-keeping”  Sometimes satellites need to change orbits  When a spacecraft has no means of propulsion, it is dead

5.  Propulsion requires reaction mass  Newton’s third law  Forcing gas out the rocket nozzle pushes the spacecraft forward  Spacecraft must carry their reaction mass with them Propulsion

6. Interplanetary Spacecraft  For interplanetary travel, a spacecraft must use its engines to leave Earth orbit  Interplanetary spacecraft fire their engines when needed to make changes in their trajectories  Between these adjustments, the spacecraft simply coasts along its orbit

7. Types of Propulsion  Most spacecraft are propelled by rockets  Launched with chemical rockets  Most use simple chemical rockets for orbital station-keeping  Some use electric or ion propulsion  Most interplanetary spacecraft use chemical rockets

8. New Propulsion Ideas  Solar sails  ~ 1 km across  Pushed by light and particles from the Sun  Nuclear propulsion  Bombs provide impulse to push the spacecraft forward (great shock absorbers!)

9. Navigation  Detects changes in geographic position, changes in velocity (speed and direction of movement), and changes in orientation An Inertial Navigation System uses a computer and motion sensors to track the position, orientation, and velocity (direction and speed of movement) of a spacecraft without the need for external references

10. Navigation with Gyroscopes  Gyroscopes measure the change in orientation of the spacecraft compared to the original orientation  Similar to the ability of a blindfolded passenger in a car to feel the car turn left and right or tilt up and down

11. Navigation with Accelerometers  Accelerometers measure the acceleration of a spacecraft  Similar to the ability of a blindfolded passenger in a car to feel himself pressed back into his seat as the vehicle accelerates forward or pulled forward as it slows down

12. Fine Guidance  For precision pointing, spacecraft use cameras to lock onto stars  Hubble can point steadily at a dime at a distance of 200 miles  Accurate pointing is important for spacecraft so that when they fire their engines, they are headed in the right direction Hubble fine guidance sensor

13. Power  Batteries  limited lifetime  Solar power  works well in inner solar system  modest power requirements, charge batteries  Small nuclear generators  necessary for long duration flights  outer solar system, where sunlight is faint Cassini’s nuclear generator

14. Communications  Telemetry  Control  Science Data NASA’s Deep Space Network communicates with spacecraft throughout the Solar System

15. Autonomous Spacecraft  Light travel time to Mars can very from 4 minutes to about 20 minutes  Light travel time to Jupiter, Saturn and beyond can take hours  Spacecraft must be able to respond to new conditions

16. But what can spacecraft do?  Imagery (optical and other wavelengths)  Radar  Chemical Analysis (surfaces, atmospheres, and in space)  Measure magnetic fields  Local conditions – temperature, pressure, density, wind speed, in space and on the “ground”  Collect samples & return

17. Imagery – More than just pictures  Images in infrared light can reveal temperature  Images in infrared light can reveal which minerals are present  Satellites in orbit can detect gamma rays from radioactive elements on planetary surfaces  Radio waves can tell surface elevation and texture of soils

18. Daytime temperatures on Mars from infrared images

19. Topographic map of Mars - Radar

20. Map of neutron emission on Mars shows frozen water under the surface

21. Minerals on Mars The mineral hematite is found using infrared images Clay minerals found using non-visible imagery

22. TO DO LIST:  Read NASA website (Oncourse)  IN-CLASS QUIZ FRIDAY!!  Activities TODAY & TOMORROW