Lectures

Question 1

InSAR and electromagnetic waves

Answer 1

• Most examine backscatter strength.
• Examines the PHASE of the return signal. Phase difference occurs on second pass, due to ice or ground motion.

InSAR can measure relative DISPLACEMENTS of a few mm from space

Question 2

Altimetry (Active Sensors)

Answer 2

Provides precise elevation of a surface by measuring travel time of a pulse (lidar or radar) to a surface.

Altimeters can also be passive.

Question 3

Resolution (Active Sensors)

Answer 3

The resolution across track is ~ equal to half the pulse length. Closer objects will be resolved as distinct objects; further ones may be perceived by the antenna as one broad object.

Question 4

How is distance measured with active microwave?

Answer 4

The distance of an object from the aircraft antenna is determined by the length of time required for the pulse of microwave energy traveling at the speed of light to reach the object and be reflected back to the antenna

Question 5

Footprint Size (Pulse-Limited vs Beam-Limited)

Answer 5

Pulse-Limited (uses pulses)
The width of the area illuminated by the leading edge of the pulse by the time the trailing edge first intersects the surface. Determined by interaction of pulse with surface.

Beam-Limited (uses beam)
The width of the area over which signal is collected by the antenna. Determined by the height of the sensor (h) and the length of the antenna (L)

Question 6

LIDAR definition

Answer 6

LIDAR (Light Detection and Ranging) is the technology of using PULSES of laser (light) striking the surfaces of the earth and measuring the time of pulse return
* Typically NIR(1064 nm) or Green (532 nm) but others do exist.

acquisition system includes:  LIDAR sensor
* GPS

Question 7

LIDAR Applications

Answer 7

ICESat mission (now failed) –lasers to measure ice elevation

Laser ranging from ground stations is used to determine orbits of satellites

• Ocean surface
• Elevation / structure of land surface
• Hydrological cycle / modeling
• Floodplain management
• Natural resource management
• 3D visualization (security)
• Site-selection
• Coastal mapping

Question 8

LIDAR Advantages

Answer 8

• Small FOV of about 1 mrad
  (0. 2 m on ground from aircraft, 50 m on ground from satellites)
• Range Resolution (~10 cm)
• No penetration in snow

Question 9

What does InSAR stand for?

Answer 9

Inteferometric Synthetic Aperture Radar (InSAR)

Question 10

Define “phase”

Answer 10

In relation to a reference signal. 0, pi/2, pi etc. Where cycles fall on 0-360 deg (360 or 2pi is complete wavelength).

Question 11

Altimetry crossovers

Answer 11

used to calibrate height between passes

Question 12

Altimetry usefulness

Answer 12

sea surface topography/height, aka El Nino or sea level rise

Question 13

Crown bulk densisty

Answer 13

via LIDAR, important for understanding how forest fires spread

Question 14

EOS program established when? First EOS satellite launch?

Answer 14

Earth Observing System, 1988

First launch in 1998

Question 15

EOS defined

Answer 15

• series of satellites
• a science component
• a data system

supporting a coordinated series of polar-orbiting and low inclination satellites for long-term global observations of the land surface, biosphere, solid Earth, atmosphere, and oceans

The overarching goal is to determine the extent, causes, and regional consequences of global climate change. THE EXTENT IS CURRENTLY UNKNOWN. Must understand both human and natural components.

Question 16

Earth Science Enterprise (ESE) started when?

Answer 16

1991, to study the Earth as a system

Question 17

Earth system science categories

Answer 17

• Sun-Earth connection
• Climate variability and change
• Earth surface and interior
• weather
• Carbon cycle and ecosystems
• Atmospheric composition
• Water and energy cycle

Question 18

MTPE

Answer 18

Mission to Planet Earth (MTPE): NASA’s Earth Science Enterprise (ESE)

Question 19

Earth System Science at NASA has three major goals:

Answer 19

1. Science: Observe, understand and model the Earth system to learn how it is changing, and the consequences for life on Earth
2. Applications: Expand and accelerate the realization of economic and societal benefits from Earth science, information, and technology
3. Technology: Develop and adopt advanced technologies to enable mission success and serve national priorities

Question 20

EOS Goals and Mission Objectives

Answer 20

GOALS
* understand earth system, and the effects
of natural and human induced changes
* Expand knowledge from points of space, aircraft, and in situ platforms
* Disseminate information
* Support environmental policy

MISSION OBJECTIVES
* Integrated observing system for
multidisciplinary study 
* Comprehensive data and information system, including retrieval . processing
* A global database 
* Improve predictive models