This document discusses active and passive remote sensing sensors. It defines sensors as devices that record reflected or emitted energy without contacting the target. Sensors are classified as active or passive, with active sensors providing their own illumination and passive sensors detecting natural energy. Examples of active sensors include RADARSAT-1 and LISS-1, while examples of passive sensors are SPOT-1 and LANDSAT-1. The key difference is that active sensors can collect data day or night, while passive sensors rely on natural illumination. Applications and advantages and disadvantages of each type are also summarized.

1. Remote Sensing Sensors
ACTIVE & PASSIVE SENSORS

2. 1. Introduction of Remote Sensing.
2. Definition of Sensors.
3. Classification of Sensors.
4. Active & Passive Sensors.
5. Examples for Active & Passive Sensors.
6. Difference between Active & Passive Sensors.
7. Advantages & Disadvantages of Active & Passive
Sensors.
8. Applications of active and passive sensors.
9. Conclusion.
10. References.

3. “Remote Sensing is the Science
(& to the some extent, Art) of
acquiring information about the earth’s
surface without actually being in
contact with it. This is done by
sensing & recording reflected or
emitted energy & processing,
analyzing & applying that information.”

4. “A sensor is a device comprising
of optical component or system
and a detector with electronic
circuitry that will be used to record
the reflected and/or emitted
energy from various objects”.

6. Active Sensors: Active Remote sensors create their
own electromagnetic energy that is transmitted
from the sensor towards the terrain, interacts
with the terrain producing a backscatter of
energy and is recorded by the remote sensor’s receiver.
Passive Sensors: Passive sensor detects the naturally
emitted microwave energy within its field of view.

7. 1) RADARSAT-1: Is an advanced Earth observation satellite project
developed by the Canadian Space Agency (CSA) on 4th
Nov 1995 to
monitor environmental change & to support resource sustainability.
RADARSAT Satellite A 3D view of flight path & data Radarsat image of
Antarctica
shown over Radarsat(600x404) (3424x2848)

8. 2) LISS-1: It is a multispectral instrument with a 76m resolution in 4
wavebands. A more advanced version of LISS, LISS-2 is carried by the IRS
-1B satellite which was launched in 1991.
LISS-1 Satellite LISS-1 Satellite image of Delhi, India LISS-1 satellite image of
Surat, India
(1000x1000) (1000x1000)

9. 1) SPOT-1: It was launched on 22nd
Feb, 1986 with 10 panchromatic &
20 meter multispectral picture resolution capability.
SPOT Satellite Spot satellite image of San Francisco SPOT satellite
image of
& the East Bay(800x717) Hong-
Kong(530x523)

10. 2) LANDSAT-1: It was launched on 23rd
July 1972, at that time the
satellite was known as the Earth Resource Technology Satellite (ERTS). It
was the first Earth observing satellite to be launched with the express
intent to study & monitor our Planet’s Landmasses.
LANDSAT-1 Satellite LANDSAT image of St.Helens LANDSAT image of Crater
Lake-Caldera
(2000x2000) (380x380)

11. Active Sensors
 Active transducers generate electric current
or voltage directly in response to
environmental stimulation.
 Active sensors provides their own energy
source for illumination.
 Active sensors are able to obtain
measurements anytime (Day & Night).
Passive Sensors
 Passive transducers produce a change in
some passive electrical quantity, such as
capacitance, resistance, or inductance, as a
result of stimulation. These usually require
additional electrical energy for excitation.
 Passive sensors can only be used to detect
energy when the naturally occurring energy
is available.
 Passive Sensors can obtain measurements
only in the Day time.

12. Advantages Disadvantages
Better control of noise sources through
control of injected signal.
Because both sources and receivers are
under the surveyor's control, he must supply
both. Therefore, field equipment tends to be
more complex
Because propagating fields are generally
measured, active experiments usually
provide better depth control over source of
anomalous signal.
Field operations and logistics are generally
more complex and time consuming than
passive experiments.
Many different source/receiver configurations
can be used allowing for a wide variety of
survey designs. This allows survey designers
great flexibility in customizing surveys for
particular problems.
Many different source/receiver configurations
can be used allowing for a wide variety of
survey designs. The increase in the number
of field options inevitably leads to greater
survey design costs and potentially to
increased probability of field mishaps.
Once set up, active experiments are capable of
producing vast quantities of data that can be used
to interpret subtle details of the earth's subsurface.
The large quantity of data obtained in many
active experiments can become
overwhelming to process and interpret.

13. Advantages Disadvantages
Surveyor need only record a naturally
occurring field; therefore, he need supply
only a sensor and a data recorder.
Less control of noise because source of the
signal is out of the control of the surveyor.
Field operations are generally very time
efficient. Thus, passive experiments can be
run over wider areas in a more cost-effective
manner.
Because passive fields are generally the
result of integrating anomalous geologic
contributions over wide areas, identification
of the source of an anomalous reading can
be difficult.
One or two well-established field procedures
are generally used. Contractors can provide
these surveys on short notice with relatively
easily quantifiable results.
One or two well-established field procedures
is generally used. This limits the amount of
customization that can be done for specific
problems.
Interpretation of the limited set of
observations can be accomplished with
modest computational requirements quickly
and efficiently.
The data sets collected in passive
experiments are smaller than those collected
in active experiments and usually do not
allow for as detailed an interpretation.

14. Radarsat: Imaging characteristics, mapping of
vegetation, vegetated terrain and sand terrain
LISS: Land use, land cover and geological
aspects
SPOT: Resources of earth and environmental
aspects
Landsat: Seasonal features like weather,
atmosphere, rainfall on images

15.  Sensor is a device comprising of optical component or
system and a detector electronic circuitry used to record
 It is a very important component in remote sensing
 Active sensors are more advantageous than passive
sensors
 LISS is one of the active sensors which is launched in
Indian satellites.
 LISS-2 is the advanced version carried by the Indian
satellite IRS-1B

16.  FLOYD F. SABINS(1996/1997) REMOTE SENSING principles and Interpretation W.H.
FREEMAN AND COMPANY NEWYORK 3rd
Edition, page 29,69,105,177,236.
 B.Bhatta(2008) Remote sensing and GIS Oxford University press, page 442,121,129,135.144
 Fundamentals of Remote Sensing A Canada Centre for Remote Sensing Tutorials Natural
Resources Canada, page 5,19.
 Websites
http://en.wikipedia.org/wiki/Radarsat-1
http://www.angelfire.com/co/pallav/sensorindia.html
en.wikipedia.org/wiki/SPOT_(satellite)
nsidc.org/data/radarsat/pdfs/RADARSAT1.pdf
galitzin.mines.edu/INTROGP/notes_te…