Imaging Data And Space Photography
From the beginning, NASA understood that space photography played a vital role in its missions. Releasing public domain images of a lonely blue planet or footage of astronauts on spacewalks elegantly communicate their accomplishments to the public while inspiring future engineers and scientists.
Imaging Data and Space Photography
Over time, photography techniques grew from pointing a camera out of a window to using powerful mirrors and telescopes to capture impossibly distant subjects. To share these images with the world, NASA needed to solve photographic and data challenges. From the original Blue Marble image to the brand new James Webb Space Telescope images, space exploration visual identity has always been powered by data.
Discoveries like radio wave imagery power many of the most common techniques used in space photography. Ultraviolet photography reveals extragalactic planets and stars by creating two-dimensional images of UV radiation. To capture images at the extremes of the light spectrum, infrared cameras focus on electrons emitting infrared radiation. And radio imaging constructs images by scanning across space, assigning each pixel image data to create a mosaic of space.
These techniques require an immense amount of imaging data to construct even a single photograph. This image of the center of the Milky Way, captured by the MeerKAT Radio Telescope in South Africa, is a composition of 20 separate radio wave observations. The 1,000 by 600 lightyear panorama required 70 terabytes of radio wave imagery data and three years of processing for the single image.
Astrophotography, also known as astronomical imaging, is the photography or imaging of astronomical objects, celestial events, or areas of the night sky. The first photograph of an astronomical object (the Moon) was taken in 1840, but it was not until the late 19th century that advances in technology allowed for detailed stellar photography. Besides being able to record the details of extended objects such as the Moon, Sun, and planets, modern astrophotography has the ability to image objects outside of the visible spectrum of the human eye such as dim stars, nebulae, and galaxies. This is accomplished through long time exposure as both film and digital cameras can accumulate and sum photons over long periods of time or using specialized optical filters which limit the photons to a certain wavelength.
Today, astrophotography is mostly a subdiscipline in amateur astronomy, usually seeking aesthetically pleasing images rather than scientific data. Amateurs use a wide range of special equipment and techniques.
With a few exceptions, astronomical photography employs long exposures since both film and digital imaging devices can accumulate light photons over long periods of time. The amount of light hitting the film or detector is also increased by increasing the diameter of the primary optics (the objective) being used. Urban areas produce light pollution so equipment and observatories doing astronomical imaging are often located in remote locations to allow long exposures without the film or detectors being swamped with stray light.
Astronomical photography was one of the earliest types of scientific photography and almost from its inception it diversified into subdisciplines that each have a specific goal including star cartography, astrometry, stellar classification, photometry, spectroscopy, polarimetry, and the discovery of astronomical objects such as asteroids, meteors, comets, variable stars, novae, and even unknown planets. These often require specialized equipment such as telescopes designed for precise imaging, for wide field of view (such as Schmidt cameras), or for work at specific wavelengths of light. Astronomical CCD cameras may cool the sensor to reduce thermal noise and to allow the detector to record images in other spectra such as in infrared astronomy. Specialized filters are also used to record images in specific wavelengths.
The beginning of the 20th century saw the worldwide construction of refracting telescopes and sophisticated large reflecting telescopes specifically designed for photographic imaging. Towards the middle of the century, giant telescopes such as the 200 in (5.1 m) Hale Telescope and the 48 in (120 cm) Samuel Oschin telescope at Palomar Observatory were pushing the limits of film photography.
The late 20th century saw advances in astronomical imaging take place in the form of new hardware, with the construction of giant multi-mirror and segmented mirror telescopes. It would also see the introduction of space-based telescopes, such as the Hubble Space Telescope. Operating outside the atmosphere's turbulence, scattered ambient light and the vagaries of weather allows the Hubble Space Telescope, with a mirror diameter of 2.4 metres (94 in), to record stars down to the 30th magnitude, some 100 times dimmer than what the 5-meter Mount Palomar Hale telescope could record in 1949.
Astrophotography is a popular hobby among photographers and amateur astronomers. Techniques ranges from basic film and digital cameras on tripods up to methods and equipment geared toward advanced imaging. Amateur astronomers and amateur telescope makers also use homemade equipment and modified devices.
Since the late 1990s amateurs have been following the professional observatories in the switch from film to digital CCDs for astronomical imaging. CCDs are more sensitive than film, allowing much shorter exposure times, and have a linear response to light. Images can be captured in many short exposures to create a synthetic long exposure. Digital cameras also have minimal or no moving parts and the ability to be operated remotely via an infrared remote or computer tethering, limiting vibration. Simple digital devices such as webcams can be modified to allow access to the focal plane and even (after the cutting of a few wires), for long exposure photography. Digital video cameras are also used. There are many techniques and pieces of commercially manufactured equipment for attaching digital single-lens reflex (DSLR) cameras and even basic point and shoot cameras to telescopes. Consumer-level digital cameras suffer from image noise over long exposures, so there are many techniques for cooling the camera, including cryogenic cooling. Astronomical equipment companies also now offer a wide range of purpose-built astronomical CCD cameras complete with hardware and processing software. Many commercially available DSLR cameras have the ability to take long time exposures combined with sequential (time-lapse) images allowing the photographer to create a motion picture of the night sky. CMOS cameras are increasingly replacing CCD cameras in the amateur sector.
Astrophotographic hardware among non-professional astronomers varies widely since the photographers themselves range from general photographers shooting some form of aesthetically pleasing images to very serious amateur astronomers collecting data for scientific research. As a hobby, astrophotography has many challenges that have to be overcome that differ from conventional photography and from what is normally encountered in professional astronomy.
There are also cameras specifically designed for amateur astrophotography based on commercially available imaging sensors. They may also allow the sensor to be cooled to reduce thermal noise in long exposures, provide raw image readout, and to be controlled from a computer for automated imaging. Raw image readout allows later better image processing by retaining all the original image data which along with stacking can assist in imaging faint deep sky objects.
With very low light capability, a few specific models of webcams are popular for Solar, Lunar, and Planetary imaging. Mostly, these are manually focused cameras containing a CCD sensor instead of the more common CMOS. The lenses of these cameras are removed and then these are attached to telescopes to record images, videos, or both. In newer techniques, videos of very faint objects are taken and the sharpest frames of the video are 'stacked' together to obtain a still image of respectable contrast. The Philips PCVC 740K and SPC 900 are among the few webcams liked by astrophotographers. Any smartphone that allows long exposures can be used for this purpose, but some phones have a specific mode for astrophotography that will stitch together multiple exposures.
From the very beginning, NASA has understood that space photography plays a vital role in its missions. By releasing images of a lonely blue planet or footage of astronauts in space, they elegantly communicate their achievements to the public and inspire future engineers and scientists.
Over time, the photography technique evolved from pointing the camera from a window to using powerful mirrors and telescopes to photograph distant objects. In order to share these images with the world, NASA had to overcome challenges ranging from imaging technology itself to data storage and transfer. From the original image of the Pale Blue Dot to new shots from the James Webb Space Telescope, the visual image of space exploration has always relied on data.
Discoveries like radio wave imaging underlie many of the most common techniques used in space photography. Ultraviolet photography allows the detection of extragalactic planets and stars by creating two-dimensional images of ultraviolet radiation. To obtain images at the other extreme of the light spectrum, infrared cameras focus on electrons emitting infrared radiation. And photography creates an images by scanning space, assigning image data to each pixel to create a mosaic of space.
These methods require a huge amount of data to create a single photo. The image of the center of the Milky Way, obtained by the MeerKAT radio telescope in South Africa, is a composite of 20 separate radio observations. It took 70 terabytes of radio wave imaging data and three years to process one image to create the 1,000-by-600-light-year panorama.
Data from satellites and cameras are collected and stored on board spacecraft. In an article for VentureBeat, the marketing director of the IoT segment of Western Digital Yaniv Yarovychi, talked about the unique challenges of data storage in space. Yarovychi emphasizes the importance of data reliability and integrity in such cases. A mission like the James Webb Space Telescope costs so much money, time and effort that it would be a shame to lose the collected data due to a failure of a disk drive drifting somewhere in space. 041b061a72