Sensors. High spatial resolution – Quickbird, IKONOS, OrbView-3, SPOT-5 PAN, IRS-P6 Medium spatial resolution – Landsat-5 TM, Landsat-7 ETM+, ASTER, SPOT

Sensors

•High spatial resolution

– Quickbird, IKONOS, OrbView-3, SPOT-5 PAN, IRS-P6

• Medium spatial resolution

– Landsat-5 TM, Landsat-7 ETM+, ASTER, SPOT

• Low spatial resolution

– MODIS, ENVISAT, GOES, AVHRR, MSS

•Pushbroom (along track) vs. Whiskbroom (across track)

• SPOT and IKONOS: Pushbroom

• Landsat: Whiskbroom

•Pushbroom scanners generally have higher radiometric resolution because they have longer “dwell time” than across-track scanners, which move laterally across landscape as they also move forward

• Most of these satellites are in sun-synchronous orbit

• The satellite passes over the same part of the Earth at roughly the same local time each day

• Its “inclination” is about 8 degrees off of polar orbit

• The fact that the earth is not a perfect sphere makes the orbital plane rotate slowly around the earth (this would not happen if it were perfectly polar)

• Slow motion of orbital plane matches the latitudinal motion of the sun in the sky over the year

• Maintains similar sun angles along its ground trace for all orbits

• That means that a given location always gets the same mean sunlight angle, which provides consistent lighting

• First started by NASA in 1972; later turned over to NOAA

• Since 1984 satellite operation and data handling are managed by a commercial company EOSAT

• LANDSAT-7 launched in 1999; developed scan line error in 2003

• Only 5 is still working; outdated

Several sensor types Multi-spectral scanner

(MSS) – LANDSAT-1 through LANDSAT-5

Thematic Mapper (TM) – LANDSAT-4 and -5

Enhanced Thematic Mapper (ETM+) – LANDSAT-7

Thematic Mapper spectral resolution

• Slightly different bands than TM; otherwise similar, stressing continuity

• Check out the movie LANDSAT-7 ETM+ BAND CHARACTERISTICS

Band Number

Nominal spectrum

Spectral Range (µ)

Ground Resolution

(m)

Data Lines Per Scan

Data Line Length (bytes)

1 Blue .450 to .515 30 16 6,600

2 green .525 to .605 30 16 6,600

3 red .630 to .690 30 16 6,600

4 Near IR .775 to .900 30 16 6,600

5 mid IR 1.550 to 1.750 30 16 6,600

6 Thermal IR 10.40 to 12.50 60 8 3,300

7 mid IR 2.090 to 2.35 30 16 6,600

8 panchromatic .520 to .900 15 32 13,200

Band Nominal Spectral location

Applications

1 Blue Water body penetration, soil-water discrimination, forest type mapping, cultural feature ID

2 Green Green reflectance peak of veg, for veg ID and assessment of vigor, cultural feature ID

3 Red Chlorophyll absorption region, plant species differentiation, cultural feature ID

4 Near infrared Veg types, vigor and biomass content, delineating water bodies, soil moisture assessment

5 mid infrared (1.55-1.75 m)

Veg moisture, soil moisture, diff of soil from clouds

6 Thermal infrared Veg stress analysis, soil moisture, thermal mapping

7 mid infrared(2.08-2.35 m)

Discriminating mineral and rock types, veg moisture

•16 day repeat cycle• Orbit takes about 99 minutes (14.5 per day)

• Follows earth’s rotation so crosses the equator at the same time (~10 a.m.)

•183 km swath width; 170 km data frame

•233 orbits per 16 days

• Extensive archive distributed by the Earth Resource Observation System (EROS) Data Center of the US Geological Survey

• Available at http://eros.usgs.gov/#/Find_Data/Products_and_Data_Available/ETM

•Satellite Pour l'Observation de la Terre operated by the French Space Agency, Centre National d'Etudes Spatiales (CNES).

•5 satellites launched 1986-2002 (several are still operational)

•Each has 2 High Resolution Visible (HRV) sensors constructed with multilinear array detectors, or “Pushbroom scanners” that record multispectral data along a wide swath

• The position of each HRV unit can be changed by ground control to observe a region of interest that is at an oblique angle to the satellite—up to ±27º relative to the vertical.

• Off-nadir viewing allows for acquisition of stereoscopic imagery (because of the parallax created) and provides a shorter revisit interval of 1 to 3 days.

• Any point on 95% of the Earth can be imaged any day by one of the satellites

• Two modes: panchromatic and multispectral

Developed by Space Imaging, launched 1999

Has sun-synchronous orbit and crosses equator at 10:30 AM

Highly maneuverable: can point at a new target and stabilize itself in seconds, enabling it to follow meandering features

The entire spacecraft moves, not just the sensors, allowing data collection at angles of up to 45°from nadir (allows for side-by-side and fore-aft stereo imaging)

Employs a linear array scanner (“pushbroom”)

11 km swath width; customizable

DigitalGlobe satellite launched in October, 2009

Very agile, and has increased on-board storage

High altitude (770 km), sun synchronous orbit

Short revisit time

8 spectral bands

16.4 km swath width

SourceSource VT VT OrthophotosOrthophotos

SensorSensor FilmFilm

Spatial Spatial ResolutionResolution

0.5m0.5m

Spectral Spectral CoverageCoverage

Radiometric Radiometric ResolutionResolution

8-bit8-bit

1

SourceSource Duchess Duchess County County OrthophotosOrthophotos

SensorSensor FilmFilm


0.62ft0.62ft



8-bit8-bit

1 1 1

SourceSource Emerge Emerge OrthophotosOrthophotos

SensorSensor Digital CameraDigital Camera


0.6m0.6m



8-bit8-bit

1 1 1

Imagery © Pictometery, 2007

38ft38ft64ft64ft


Pan: 1mPan: 1m

MS: 4mMS: 4m


Radiometric Radiometric ResolutionResolution 11-bit11-bit

Temporal Temporal ResolutionResolution 3-4 days3-4 days

Scene SizeScene Size 13 x 13km13 x 13km

1 1 1 1

1

Source: Space Imaging

www.spaceimaging.com

Tsang Po River, Tibet – 1m Panchromatic

Woodstock, VT– 1m Panchromatic Waitsfield, VT– 4m Multispectral

© Space Imaging© Space Imaging


Pan: 61cm - 72cmPan: 61cm - 72cm

MS: 2.44m – MS: 2.44m – 2.88m2.88m



Temporal Temporal ResolutionResolution 3-4 days3-4 days


1 1 1 1

1

www.digitalglobe.com

Source: DigitalGlobe

Manhattan, NY – 0.61m Multispectral



Boston, MA – 0.61m Panchromatic

Mauritius – 2.44m Multispectral


Pan: 50cmPan: 50cm

MS: 1.8m – 2.4mMS: 1.8m – 2.4m



Temporal Temporal ResolutionResolution 1.1-3.7 days1.1-3.7 days


1 1 1 11 1

1


Deepwater Horizon clean up– 0.5m Multispectral

1



Boulder, CO – 0.5m Multispectral Deepwater Horizon – 0.5m Multispectral


Pan: 15mPan: 15m

MS: 30m/60mMS: 30m/60m



Temporal Temporal ResolutionResolution 16 days16 days


1 1 1 11 2

1

Brattleboro, VT – 30m Multispectral

Harriman Reservoir, VT – 30m Multispectral St. Albans Bay, VT – 30m Multispectral

Spatial Spatial ResolutionResolution MS: 15m/30m/90mMS: 15m/30m/90m


Radiometric Radiometric ResolutionResolution 8-bit/12-bit8-bit/12-bit

Temporal Temporal ResolutionResolution VariesVaries

Scene SizeScene Size 60x 60km60x 60km

1 1 51 6

Boston, MA – 90m Thermal

Winooski River, VT – 15m Multispectral Otter Creek, VT – 15m Multispectral

Documents

Sensors. High spatial resolution – Quickbird, IKONOS, OrbView-3, SPOT-5 PAN, IRS-P6 Medium spatial resolution – Landsat-5 TM, Landsat-7 ETM+, ASTER, SPOT