ES 771 Lecture 4

ES 771 Lecture
James S. Aber

MANNED SPACE PHOTOGRAPHY

**Table of Contents**
Early photography	Shuttle photography
Space station	References

Early Manned Space Photography

U.S. manned space photographs of the Earth began with the Mercury, Gemini, and Apollo missions of the 1960s and early 70s. Many spectacular images of the lands, oceans, and atmosphere were obtained, and these demonstrated the potential of synoptic space photography for various earth science investigations. With few exceptions, these photos were taken at the discretion of astronauts, who had little formal background in either earth science or photography.

Systematic manned space photography was undertaken during the Skylab missions of 1973 and 1974. Skylab was a orbiting space station that was utilized for extended Earth observations (Wilmarth et al. 1977). The overall objectives were to determine the quality and quantity of photographic and observational data that could be collected by astronauts with benefit from preflight training and ground support during flight. It was recognized that astronauts needed much additional preflight scientific and operational training to take multidisciplinary photographs (Wilmarth et al. 1977). Skylab 4 was most successful; about 2000 photographs were obtained of more than 850 features and phenomena. The lessons learned during Skylab missions formed the basis for the program of space-shuttle photography in the 1980s and '90s.

See MRS--Platform, Skylab.

Space Shuttle Photography

Astronauts on space-shuttle missions have taken to date (6/98) more than 300,000 photographs with hand-held cameras. A large portion of these are Earth-looking images that provide unique views of the world's surface features: deserts, volcanoes, coasts, mountains, oceans, glaciers, sea ice, rivers, lakes, dust, fires, clouds, human settlement, agriculture, and many other features. Space-shuttle photographs are taken in all possible orientations for a greater range of perspectives than is possible with any unmanned satellite instruments. Different viewing positions are demonstrated for Chicago and Lake Michigan in the following examples.

Near vertical	View straight down to Earth's surface.
Low oblique	View toward side--horizon not visible.
High oblique	View toward side--horizon visible.

Space-shuttle photography is the result of systematic Earth and environmental science training given to each astronaut crew prior to flight. Much of the photography consists of revisits to targets previously photographed. Each day during flight, astronauts are given instructions for photographs based on cloud-cover and orbital conditions. Astronauts are also free to take photographs of any interesting or attractive scenes. Special advantages of astronaut photography include (Lulla et al. 1993) the following.

Images are taken at various sun angles, ranging from negative angles (below horizon) to nearly vertical. This provides for unique views under various lighting conditions that are not available with other remote sensing systems.
Sequential (overlapping) near-vertical photographs with different vantage points provide for stereoscopic viewing. Sequential photos can be mounted into mosaics.
Little-known tropical areas are well represented in the photography database. These regions are undergoing very rapid human-induced environmental transformations.

Various cameras, lenses, and film types are employed for space-shuttle photography. Hasselblad cameras are most commonly used. The Hasselblad takes pictures with 70-mm (2¾-inch) format film. Lenses vary from 40 mm to 250 mm focal length. For a near-vertical photo at 300 km altitude, a typical altitude for space-shuttle missions, the 100-mm lens covers a ground area 163 km across. The 250-mm lens photographs an area 65 km wide. The Linhof camera is also utilized on most missions. The Linhof takes 125-mm (5-inch) format film. Other still cameras that have been used include: Rolleiflex (70 mm), Nikon (35 mm), and the large-format camera. IMAX and 16-mm movie footage are taken on some flights along with video imagery.

See MRS--Sensor, LFC.

Film selection for space-shuttle photography is relatively conservative. Films utilized most often are Kodak 5017/6017 Professional Ektachrome (color visible) and Kodak Aerochrome 2443 (color infrared). Other special film types are employed rarely. Most photographs have been digitized and converted to video format. "Digitization, rectification, multi-layering (GIS), classification, and mensuration of these digitized analog images is now fairly routine ..." (Lulla et al. 1993). Examples of film types are given below in low-oblique views for the Island of Hawaii.

Color visible	Normal color film sensitive to blue, green and red light.
Color infrared	Color-IR film sensitive to green, red, and near-infrared energy.

The electronic still camera (ESC) is a charged-couple device that produces near-film-quality images in digital format. It has been utilized routinely on missions since 1991. The ESC system has three components: (1) hand-held fully digital and programmable, high-resolution camera, (2) lap-top computer for onboard image processing and downlink, and (3) ground station for reception, processing, and distribution of digital data and images (Lulla and Holland 1993). The camera can operate a 2048x2048 black-and-white pixel array or a 1024x1024 array for three-band color and color-infrared. Current spectral response range is 0.4 to 1.1 µm, which is significantly greater than films now in use.

The ground coverage of space-shuttle photography is determined by factors of orbit geometry that vary with each mission. The most important factor is orbit inclination, ±28.5° for most missions, which limits photographs to low-latitude locations. This includes about one-half of the Earth's surface, an area with more than 75% of the world's human population. Orbital inclinations from ±34.3° to a maximum of ±57° are used on some special missions. For the latter, regions up to around ±60° latitude can be photographed in low-oblique views. High-latitude areas above the Arctic and Antarctic circles are photographed only rarely in high-oblique views.

See MRS--Platform, Space shuttle.

Time of launch and crew sleeping schedules affect the times of daylight when photographs may be acquired, as very few pictures are taken on the Earth's night side. Thus, some missions return pictures mainly from the northern hemisphere, whereas other missions take photos mostly in the southern hemisphere. An important factor is cloud cover that often obscures ground features of interest. For example, many sites have few or no cloud-free photographs. Photography is not the primary objective on most space-shuttle flights, so pictures are taken when astronauts are not busy with other duties. The result of these factors is very uneven coverage of the world by space-shuttle photography.

Space-shuttle photography has been utilized for several global-change studies (Lulla et al. 1991). These include monitoring of inland water bodies in climatically sensitive areas: Great Salt Lake, Aral Sea, Lake Chad, etc. Photographs have also been used to document changes in deltaic and estuarine environments, for example the Omo delta of Lake Turkana. Space-shuttle photographs are also valuable for studies of ephemeral events, such as volcanic eruptions and dust, auroras, and dust storms. Color-infrared photographs are useful for establishing biomass (vegetation).

Smoke from natural or man-made fires is a feature of special interest. Compared to other forms of space-based remote sensing, space-shuttle photography excels for imaging smoke from burning biomass (Glasser and Lulla 1998). Space-shuttle photography proved especially valuable for monitoring oil-field fires during the Kuwait War (Lulla and Helfert 1991). Pictures were acquired during two shuttle missions in April and May of 1991.

The presence of human photographers in space has demonstrated some important capabilities to:

Observe and respond quickly to unusual ground events or lighting conditions.
Preselect and acquire scientifically useful images.
Photograph phenomena from different look angles with different cameras, lenses, and films.

"These qualities demonstrate the value of a human observer in orbit in adding to understanding of our planet Earth, and interacting with ground scientists in real time to acquire data and confirm or deny events." (Lulla and Helfert 1991) These capabilities may increase greatly with operation of the orbiting space station in the 21st century.

International Space Station

During the period 1995-98, Shuttle/Mir missions paved the way for development of a permanently manned space station. Known as International Space Station, Phase 1, more than 20,000 new photographs were acquired during these missions. Most of the images are not yet cataloged (Glasser and Lulla 1998).

The international space station has become operational early in the 21st century. It includes a nadir window dedicated to Earth observation experiments. This window is a multilayer composite, for which the optical properties may be changed. It facilitates high-quality remote sensing in the visible, near-infrared, and mid-infrared portions of the spectrum. Equipment racks around the window provides support, power, and communciations for various kinds of cameras and sensors. The space station also has external mounts for securing remote sensing devices outside the hull.

Continuous, long-term operation of the space station provides unparalleled opportunity for Earth observation. The space station orbits at inclination ± 51.6°, which covers more than 75% of the Earth's surface, containing 95% of the human population. Beneath this orbit, every ground locality is revisited each three days. Earth-observation experiments are now underway, and many kinds of scientific missions are anticipated (Lulla, 1998, pers. com.).

Further Information on
Space Photography
Johnson Space Center--Imagery Services
NASA Image eXchange--NIX
International space station Nearly a quarter million photos
Shuttle/Mir missions

References

Glasser, M. and Lulla, K. 1998. Evidence of change in the boreal forests using NASA astronaut photography: The case for international space station earth observations. Proceedings, 27th International Symposium on Remote Sensing of Environment, p. 282-287.
Lulla, K. and Helfert, M. 1991. Smoke palls induced by Kuwaiti oilfield fires mapped from space shuttle imagery. Geocarto International 6/2:71-80.
Lulla, K.P., Helfert, M.R., Amsbury, D.L. et al. 1991. Earth observations during space shuttle flight STS-41: Discovery's Mission to Planet Earth. Geocarto International 6/1:69-80
Lulla, K., Helfert, M., Evans, C., Wilkinson, M.J., Pitts, D. and Amsbury, D. 1993. Global geologic applications of space shuttle Earth observations photography database. Photogrammetric Engineering and Remote Sensing 59:1225-1231.
Lulla, K. and Holland, S.D. 1993. NASA electronic still camera (ESC) system used to image the Kamchatka volcanoes from the space shuttle. Inter. Journal Remote Sensing 14:2745-2746.
Wilmarth, V.R. et al. 1977. Skylab explores the Earth. NASA Special Publication 380, 517 p.

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