CEE 6150: Digital Image Processing 1 W. Philpot, Cornell University Satellite/Aircraft imaging systems

Satellite/Aircraft Imaging Systems Imaging Sensors

Standard scanner designs Image data formats

CEE 6150: Digital Image Processing 2 W. Philpot, Cornell University Satellite/Aircraft imaging systems

CEE 6150: Digital Image Processing 3 W. Philpot, Cornell University Satellite/Aircraft imaging systems

CEE 6150: Digital Image Processing 4 W. Philpot, Cornell University Satellite/Aircraft imaging systems

Typical whiskbroom scanner geometry

Scanning design to improve dwell time: whiskbroom scanners

Banding from Whiskbroom Scanner

Differences in calibration of individual detectors

Differences in calibration associated with scan direction

CEE 6150: Digital Image Processing 5 W. Philpot, Cornell University Satellite/Aircraft imaging systems

http://www.asprs.org/a/publications/proceedings/pecora16/Storey_J.pdf

Spectral Band Selection: Landsat 5 (TM) and Landsat 7 (ETM+)

TM Focal Plane Array http://ltpwww.gsfc.nasa.gov/IAS/handbook/handbook_htmls/chapter3/chapter3.html

CEE 6150: Digital Image Processing 6 W. Philpot, Cornell University Satellite/Aircraft imaging systems

PUSHBROOM SCANNERS:

Scanner geometry: SPOT

Spatial Resolution (SPOT) (Since 1986)

Mode Spectral Band Res. Multispectral (XS) SPOT 1,2,3,4,5 1 (Green) 0.50-0.59 µm 20 m 2 (Red) 0.61-0.68 µm 20 m 3 (Near IR) 0.79-0.89 µm 20 m SPOT 4,5 4 (Mid IR) 1.57-1.71 µm 20 m Panchromatic (P) SPOT 1,2,3 0.51-0.73 µm 10 m SPOT 4 0.61-0.68 µm 10 m SPOT 5 0.48-0.68 µm 2.5 m* Swath width @ nadir: 60 km * The panchromatic band uses two 5 m sample arrays offset by 2.5 m in both the cross-track and along-track directions. This

results in a quasi-2.5 m sample spacing, but with a resolution cell size of 5 m.

CEE 6150: Digital Image Processing 7 W. Philpot, Cornell University Satellite/Aircraft imaging systems

IKONOS (Space Imaging) Multispectral spatial dynamic Band Spectral Range (FWHM) Res. range 1 445 – 516 nm (Blue) 4 m 11 bits 2 506 – 595 nm (Green) 4 m 3 632 – 698 nm (Red) 4 m 4 757 – 853 nm (NIR) 4 m

Panchromatic spatial dynamic Spectral Range (FWHM) Res. range 445 – 900 nm (Blue) 1 m 11 bits swath width @ nadir: 10 km

Spectral Band Selection: QuickBird Multispectral spatial dynamic Band Spectral Range (FWHM) Res. range 1 450 – 520 nm (Blue) 2.44 m 11 bits 2 520 – 600 nm (Green) 2.44 m 11 bits 3 630 – 690 nm (Red) 2.44 m 11 bits 4 760 – 900 nm (NIR) 2.44 m 11 bits Panchromatic spatial dynamic Spectral Range (FWHM) Res. range 445 – 900 nm (Blue) 0.61 m 11 bits swath width @ nadir: 16.5 km

Spectral Band Selection: WorldView-2 Multispectral nadir dynamic Band Spectral Range (FWHM) Res. range 1 400 – 450 nm (Coastal) 1.84 m 11 bits 2 450 – 510 nm (Blue) 1.84 m 11 bits 3 510 – 580 nm (Green) 1.84 m 11 bits 4 585 – 625 nm (Yellow) 1.84 m 11 bits 5 630 – 690 nm (Red) 1.84 m 11 bits 6 705 – 745 nm (Red Edge) 1.84 m 11 bits 7 770 – 895 nm (NIR 1) 1.84 m 11 bits 8 860 – 1040 nm (NIR 2) 1.84 m 11 bits 2.08 m @ 20° off-nadir Panchromatic445 – 900 nm (Panchromatic) 0.46 m 11 bits swath width @ nadir: 16.4 km 0.52 m @ 20° off-nadir

Operational Land Imager (OLI; Landsat 8) Spectral bands: http://landsat.gsfc.nasa.gov/?p=5771 Focal plane array: balticbloom_oli_2015223_lrg.jpg

Web Resources Satellite Imaging Corporation: High resolution commercial systems; system descriptions and access to imagery (for purchase). http://www.satimagingcorp.com/satellite-sensors/geoeye-1.html U.S. Government image data: Access to imagery (free, mostly); includes data descriptions

http://earthexplorer.usgs.gov/ http://glovis.usgs.gov/

CEE 6150: Digital Image Processing 8 W. Philpot, Cornell University Satellite/Aircraft imaging systems

System Specs: AVIRIS (Visible-IR Imaging Spectrometer (AVIRIS) Data Rate: 17 Mbps through 1994, 20.4 Mbps from 1995. Bit depth: 10 bit through 1994, 12 bit from 1995. Detectors: Silicon (Si) for the visible range, indium-antimonide (InSb) for the NIR Scanning: "Whisk broom", 12 Hz scanning rate Spectral: 10 nm bandwidth, 0.38-2.5 µm (224 bands) Spatial: @ 20 km: 30 m GIFOV

Color Pixel misregistration (design dependent)

Color pixels along the edge of the road are due to nearest-neighbor resampling of different spectral bands when the

color registration is imperfect.

Scanner geometry: Hyperspectral

2-D CCD arrays

flight path H

θ

H sec θ

IFOV

ω

folding mirror (static)

diffraction grating

2-D array

CEE 6150: Digital Image Processing 9 W. Philpot, Cornell University Satellite/Aircraft imaging systems

Color Representation in Digital Cameras Bayer Pattern

• Digital Cameras have only one 2-D array • A color filter array (CFA) is placed between the lens and the sensors. • A CFA typically has one color filter element for each sensor. • The Bayer pattern uses the three additive

primary colors, red, green and blue (RGB), for the filter elements arranged in a 2x2 pattern..

Fuji X-trans color array (new) http://www.fujifilmusa.com/products/digital_cameras/x/fujifilm_x_pro1/features/

• Higher degree of randomness with an array of 6 x 6 pixel units. • Without using an optical low-pass filter, moire and false colors are minimized while retaining high resolution. • Inspired by the natural random arrangement of the fine grains of silver halide in film.

Fovean cameraThe layers of silicon take advantage of the fact that silicon absorbs different colors of light at different depths, so one layer records red, another layer records green and the other layer records blue.

1) lens, 2) low pass filters, 3) array

CEE 6150: Digital Image Processing 10 W. Philpot, Cornell University Satellite/Aircraft imaging systems

CEE 6150: Digital Image Processing 11 W. Philpot, Cornell University Satellite/Aircraft imaging systems

Orbital Mechanics The orbital speed of a body, in our case, a satellite, is the speed at which it orbits around the earth. Here, for simplicity, we consider only circular orbits and Newton's laws (nothing about energy or momentum). We further assume that only two objects (the earth and the satellite) need to be considered and that the mass of the satellite is negligible relative to the mass of the earth. In this case, the centripetal force, Fc, acting to drive the satellite away from the earth, and the gravitational force, Fg, attracting the satellite toward the earth, must balance exactly. Thus, if ms is the mass of the satellite, me, is the mass of the earth, G is the universal gravitational constant, and r is the distance from the center of the earth to the satellite, then:

2

2;s s ec g

m v Gm mF Fr r

= = eGmvr

⇒ =

where r = re + h (the radius of the earth + the altitude of the satellite). An object moving faster than circular velocity will enter an elliptical orbit with a velocity at any point determined by Kepler's laws of planetary motion. If the object moves faster still, it will travel at escape velocity along a parabolic orbit or beyond escape velocity in a hyperbolic orbit.

Orbital Period The orbital period of a small body orbiting a central body in a circular or elliptical orbit is:

The radium of the earth, re=6.378x106m The standard gravitational parameter, μ = Gme=3.986x1014m3s-2

Orbital families

• LEO: low earth orbit, typical altitude < 2000 km o space shuttle o space station o Hubble Space Telescope o iridium o remote sensing: EROS, Landsat o communications: email, text messaging, paging

• MEO: medium earth orbit, typical altitude 10,000 to 20,000 km o GPS: Global Positioning System

• GEO: geosynchronous earth orbit, seven earth radii, one-ninth of the distance to the moon,

altitude = 36,000 km o GOES - Geosynchronous (Geostationary) Operational Environmental Satellites o communication:

signal relays for terrestrial broadcast and cable systems direct broadcast satellite TV and radio

o TDRS: Tracking and Data Relay Satellite

32

e

rTGm

π=