Exercise 7: Active Microwave Satellites

Subject: Principles of Cartography

Course Code: Geog 2003

Instructor: Dr. M. M. Yagoub

List the main types of satellites?

1. Communication (e.g. Thuraya of UAE)

2. Meteorology (e.g. NOAA of USA)

3. Global Positioning System (GPS)

4. Land Observation satellites (Optical, Microwave)

What is the difference between active and passive sensor?

Active sensor generates its own energy e.g. flash from a camera and RADAR

Passive depends on the sun’s radiation or emission from objects (thermal)

What is the concept of active microwave?

The concept of active microwave or RADAR is that an energy pulse is sent out from an antenna and the return signal (if any) is recorded. In essence this is similar to a camera flash.

List two advantages of active remote sensing?

1. Penetration of cloud (suitable for rainy climate)

2. Independent on the sun (it can work day and night)

List two disadvantages of active remote sensing?

1. Radar images usually contain considerable high frequency noise (salt and pepper appearance)

2. They are geometrically distorted.

List the three main electromagnetic spectrums used in remote sensing?

1. Visible (0.4-0.7 um)

2. Infrared (0.7 um- 1mm)

3. Microwave (1mm – 1 m)

List the basic characteristics of the European Remote Sensing Satellite (ERS-2)

• Launched in 1995 at an altitude of 785 km, an inclination of 98.5 deg, Near-circular, polar, Sun-synchronous and ground swath width 80 Km

• Onboard sensors: Synthetic Aperture Radar (SAR) with resolution 20-30m, Scatterometer (Wind), Radar altimeter (sea depth), and Global Ozone Monitoring Experiment (GOME)

• Temporal resolution (Repeat cycle: 3-day, 35-day and 176-day)

List the basic characteristics of the Japanese Earth Resource Satellite JERS-1

· Launched in 1992 in a sun synchronous orbit at an altitude of approximately 570 km and inclination of approximately 98 deg

· Period : Approx. 96 min.

· Recurrent period : 44 days

· Onboard sensors are SAR (Synthetic Aperture Radar), which is an active microwave sensor, and OPS, an optical sensor that measures light reflected from the earth's surface ranging from visible light to short wave infrared light

Describe briefly the basic characteristics of RADARSAT

See http://www.ccrs.nrcan.gc.ca/ccrs/tekrd/radarsat/rsate.html

• RADARSAT is Canada's first series of remote sensing satellites, starting with RADARSAT-1 launched in 1995 and followed by RADARSAT-2, planned for launch in 2002.

• These satellites focus on the use of radar sensors in order to provide unique information about the Earth's surface through most weather conditions and even darkness