Today’s APOD

Read NASA website: solarsystem.nasa.gov

IN-CLASS QUIZ THIS FRIDAY!!Solar Lab, Kirkwood, Rooftop this

week

The Sun Today

A100 Solar SystemSpacecraft

Events this week

AFTER CLASS – SOLAR LAB2:30-3:30

TONIGHT - Kirkwood Obs8:30-10:30 PM

TOMORROW – Thursday – Rooftop8:30 PM Swain West

WEATHER PERMITTING

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!

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

Propulsion requires reaction mass

Newton’s third lawForcing gas out the

rocket nozzle pushes the spacecraft forward

Spacecraft must carry their reaction mass with them

Propulsion

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

Types of Propulsio

n

Most spacecraft are propelled by rocketsLaunched with chemical rockets Most use simple chemical rockets for

orbital station-keepingSome use electric or ion propulsion Most interplanetary spacecraft use

chemical rockets

New Propulsion

Ideas

Solar sails~ 1 km acrossPushed by light and particles from the Sun

Nuclear propulsionBombs provide impulse to push the spacecraft

forward (great shock absorbers!)

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

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

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

Fine GuidanceFor 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

PowerBatteries

limited lifetimeSolar power

works well in inner solar systemmodest power requirements, charge

batteriesSmall nuclear generators

necessary for long duration flightsouter solar system, where sunlight is faint

Cassini’s nuclear generator

CommunicationsTelemetryControl Science Data

NASA’s Deep Space Network communicates with spacecraft throughout the Solar System

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

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

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

Daytime temperatures on Mars from infrared images

Topographic map of Mars - Radar

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

Minerals on MarsThe mineral hematite is found using infrared images

Clay minerals found using non-visible imagery

TO DO LIST:

Read NASA website (Oncourse)

IN-CLASS QUIZ FRIDAY!!

Activities TODAY & TOMORROW