The spacecraft itself is rather compact for such a large telescope. The current design calls for a length of 6 meters and a width of 2.5 meters. Unlike the usual configuration of solar panels extending outward like "wings", SNAP's solar panels will lie along the body of the spacecraft. This simplifies the design and makes the panels more reliable.
SNAP's orbit will place it at a gravitational balance point between the Sun and the Earth, located about 1.5 million kilometers (1 million miles) from the Earth in the direction away from the Sun. This region, called the L2 Lagrange point (or colloquially as a "halo orbit") has many advantages. For one, very little fuel is needed to keep the spacecraft in position.the combined gravity of the Earth and Sun act to keep the spacecraft in place, much like a ball sitting at the bottom of a groove.
Also, at L2 the telescope can be "thermally stable". Since the Sun shines on it all the time, the temperature does not change much, putting less stress on the telescope and optics (as opposed to low-Earth orbit, where the spacecraft experiences 18 sunrises and sunsets every day). The relatively remote placement of the spacecraft also makes it easier to eliminate sources of stray light entering the telescope, since the Earth, Sun, and Moon will always be in the same area of sky as seen by SNAP, making it easier to baffle the telescope.
The detectors are near-infrared (NIR) sensors and visible light charged-coupled devices (CCDs). The CCDs are similar to what are used in retail digital cameras. However, unlike their earthbound cousins, the CCDs on SNAP are far more sensitive to light, and produce much higher quality images. Each infrared detector is 2048 x 2048 pixels (4.2 megapixels). Each visible light CCD is 3512 x 3512 pixels (12.3 megapixels). This means SNAP will be like a 600 megapixel camera!
SNAP's field of view is truly huge: each image it takes will be about a square degree, or four times the size of the full Moon. Hubble, for comparison, has a maximum field of view of only 1/400th that size. This will allow SNAP to look at a large part of the sky at once. Since SNAP is designed as a survey telescope, the wide field of view greatly enhances its abilities versus other observatories.
The visible and infrared CCDs together will detect light from about 350 nanometers (roughly blue) to 1700 nanometers (well into the infrared). There are 6 different filters used for the visible light CCDs and three for the infrared. This means that SNAP will have color vision, allowing scientists to better study the type of light emitted by astronomical targets.
SNAP's resolution (the ability to distinguish between two closely-spaced objects) will be about 0.2 arcseconds in the visible and 0.3 arcseconds in the infrared. An arcsecond is 1/3600th of a degree (for comparison, a person with typical "good" eyesight can distinguish objects as small as about sixty arcseconds, meaning SNAP's vision will be very sharp, about the same resolution as the Hubble Space Telescope.
For more technical data on the filter and CCDs, please see the