History of Remote Sensing given on the 28th of
January 2004 and presented by Dr. Bill Emery
Summary of this presentation written by John Marshall with all pictures and
slides provided by Dr. Emery
Sensores en el Óptico y en el Infrarrojo
Felix Tournachon takes a picture of Paris, 1868
In his presentation on The History of Remote Sensing Dr. Emery began
with the beginnings of remote sensing, from simple black and white photography
to the sophisticated satellites we have today. In its beginning remote sensing
was rudimentary as seen in the following slide showing a camera mounted on a
kite, yet it provided a new way at looking at the world and a glimpse of what
was to come.
Sensores en el Óptico y en el Infrarrojo
Kite Mounted Camera for Aerial Photo
The early advances in remote sensing came not so much with the sensor
but with what got the sensor to its “remote” location. These advances consisted
of simple ingenuity; putting cameras on pigeons and kites, to new technology
such as rockets that would enable cameras to one day be put in orbit.
Sensores en el Óptico y en el Infrarrojo
First Rocket Photos by Samueal Goddard in 1926
Sputnik, launched by the former USSR broke open not only the space race
but also created a new era for remote sensing.
Sensores en el Óptico y en el Infrarrojo
The world changed with the launch of Sputnik in 1956
America would follow close behind with there first remote sensing satellite
called the Television and Infrared Observation Satellite or TIROS-1 launched in
1960.
Sensores en el Óptico y en el Infrarrojo
TIROS Satellite
As Dr. Emery pointed out, most polar orbiting satellites where and still are
launched from the west coast. Since the earth rotates under the launcher from
east to west once it leaves the ground, water (Pacific Ocean) is below the launch
vehicle during its initial and critical stage of flight where if there was a failure it
would simply and safely fall into the ocean. As can be seen on the above slide,
the solar panels are placed around the satellite, which is indicative of a spin
stabilized satellite. The camera can be seen pointed along the axis of the spin
but the problem was that the sensor was not pointed at the earth all of the time
but instead sometimes pointed into space.
Sensores en el Óptico y en el Infrarrojo
This was improved upon in the next TIROS satellite by putting the sensor
so it pointed through the solar panels, rotating with the satellite (perpendicular
to the axis of spin) which allowed more of the earth to be viewed. These
satellites were commonly referred as ESSA satellites which was the predecessor
to NOAA.
Sensores en el Óptico y en el Infrarrojo
In order to receive the data, large antennas were set up to receive the
signals from the satellites and then the data would be converted for analysis.
Eventually though the size on the antennas began to shrink as it was realized
that large antennas where not necessary. Dr. Emery also pointed out that since
the early images were analog they had to be processed by hand. Below is the
first global picture of the world’s weather ever produced. Simple VHF antennas
where then added to aid meteorologists in receive the data.
Sensores en el Óptico y en el Infrarrojo
Eventually technology progressed even further to a three-axis stabilized
satellite which came as a result of the cold war. The main earth observation
satellite to introduce this technology was ITOS or Improved TIROS Operational
System. This was great because the sensor could for the first time point always
to the earth yet this also presented a new problem which had to be solved.
Since the satellite was no longer rotating it did not distribute the heat from the
sun across the entire satellite causing one side to be cold while the other was
hot. This was solved through the addition of a gold heat blanket that would
protect the satellite from over heating on one side.
It wasn’t all that bad though, a big advantage was that for the first time
solar panels could be pointed towards the sun at all times. An additional point
about the ITOS satellite was that it carried a radiometer. As Dr. Emery points
out, the difference between a radiometer and a camera is that a radiometer
collects radiation line by line rather than all at once as a camera does.
The next is next slide shows the Nimbus satellite which operates on the
same principle.
Sensores en el Óptico y en el Infrarrojo
As technology advanced such as the introduction of gyros, so did the
weight of the equipment that supported the new advances.
Sensores en el Óptico y en el Infrarrojo
•TIROS satellites weighed about 150 kg.
•ESSA Wheel satellites weighed about 250 kg.
•ITOS satellites jumped up to about 400 kg.
•Today’s NOAA and DMSP satellites weigh about 1500 kg.
The TIROS-N satellite or TIROS next generation represented a huge step
forward in that it was a fully digital system. TIROS-N carried both a Space
Environment Monitoring (SEM) suite which included a Solar Backscatter
Ultraviolet (SBUV) sensor (Emery slide). TIROS-N satellites also carried the
AVHRR sensor or Advanced Very High Resolution Radiometer. The AVHRR is
simply a scanning radiometer which senses radiation in the visible, near-infrared,
and thermal infrared. It started as a four channel sensor but is currently up to
six channels. This sensor which was carried on the TIROS N satellites is still in
use today aboard the NOAA POES satellites.
Sensores en el Óptico y en el Infrarrojo
Spc Rg
(mm)
Dector
Res (km)
IFOV (mr)
S/N@5%
NedT @
300K
MTF @
1.9 km
Tmp Rng
(K)
Ch. 1
Ch. 2 Ch. 3A Ch. 3B Ch. 4
Ch. 5
0.58-0.68 .725-1.0 1.58-1.64 3.55-3.93 10.3-11.3 11.5-12.5
Silicon
1.09
1.3 sq.
>=9:1
Silicon InGaAs
1.09
1.09
1.3 sq. 1.3 sq.
>=9:1
>=20:1
InSb
1.09
1.3 sq.
HgCdTe HgCdTe
1.09
1.09
1.3 sq. 1.3 sq
-
-
-
-
-
-
<=.12K
<=.12K
<=.12K
>.30
>.30
>.30
>.30
>.30
>.30
-
-
-
180 - 335 180 - 335 180 - 335
AVHRR Sensor Table
Along with NOAA’s POES satellites there is the Defense Meteorological
Satellite Program (DMSP) which is very similar in terms of its bus when
compared to the NOAA POES satellites. The goal of DMSP satellites is obviously
to serve the military but they also work with the POES satellites in gathering
earth observation data. The main differences between the two systems are with
their sensors. One difference is that on the DMSP satellites you have the
Operational Line Scanner, which is not as good as the AVHRR but has the added
capability of being able to pick up data at night.
So where are we headed now? In a word, NPOESS or National Polarorbiting Operations Environmental Satellite System. Basically the goal is to
merge NOAA and DMSP satellites into one group. With a cost of 10 billion
dollars, NPOESS will combine NASA, NOAA, and Department of Defense (DOD)
satellites into one program and provide one place in which to obtain data. NASA
will have the overall responsibility while DOD will be in charge of procurement.
This change was probably born out of financial reasons and poses many
questions for the remote sensing community. Some of the worries include
validation problems that may exist plus data dissemination issues. Another
words, can you get timely data from the DOD in 24 hours or less. In terms of
data validation as Dr. Emery points out, data is only as good as the calibration
prior to launch and the validation after. Of course this won’t be the only Earth
Observation effort going on in the world. The Europeans have there METOP
program which while similar does have different instruments.