Sentinel (space telescope)
Sentinel is a space observatory that Ball Aerospace is developing for the private non-profit philanthropic B612 Foundation, which is dedicated to the protection of Earth from asteroid strikes: Sentinel is B612's first spacecraft to tangibly address that mission. It will locate 90% of the asteroids greater than 140 metres (460 ft) in diameter in near-Earth orbits,
and it will follow a Venus-like orbit (i.e. between Earth and the Sun) therefore viewing the sky's night half every 20 days and seeing objects that are often difficult, if not impossible, to see in advance from Earth. Sentinel will operate for 5-and-a-half years
The B612 project grew from a one-day workshop on asteroid deflection that Piet Hut and Ed Lu at NASA Johnson Space Center, Houston, Texas on October 20, 2001 organized. Participants Rusty Schweickart, Clark Chapman, Piet Hut, and Ed Lu established the B612 Foundation on October 7, 2002. The Foundation originally planned to launch Sentinel ere December 2016 and begin data retrieval ere 6 months after successful positioning. In April 2013, the plan had moved out to launching on a SpaceX Falcon 9 in 2018, following preliminary design review in 2014, and critical design review in 2015.
As of April 2013[update], B612 is attempting to raise approximately $450 million for the total development and launch cost of Sentinel--at some $30 to $40 million per year. That funding profile excludes the advertised 2018 launch date.
Sentinel is anticipated to detect 90% of the asteroids greater than 140 meters in diameter that exist in Earth's orbit, which pose existential risk to humanity. The B612 Foundation estimates that approximately half a million asteroids in Earth's neighbourhood equal or exceed the one that struck Tunguska in 1908. It is planned to be launched atop the Falcon 9 rocket designed, manufactured by the private aerospace company SpaceX in 2016, and manoeuvred into position with the help of the gravity of Venus. Its data will be provided through an existing network of scientific data-sharing that includes NASA and academic institutions such as the Minor Planet Center in Cambridge, Massachusetts.
The telescope measures 7.7 metres (25 ft) by 3.2 metres (10 ft) mass 1,500 kilograms (3,300 lb) and will orbit the Sun at a distance of 0.6 to 0.8 astronomical units (90,000,000 to 120,000,000 km; 56,000,000 to 74,000,000 mi) approximately the same orbital distance as Venus. It will employ infrared astronomy methods to identify asteroids against the cold of outer space. The B612 Foundation is working with Ball Aerospace to construct Sentinel's 0.51 m (20 inches) aluminum mirror, which will capture the large field of view. "Sentinel will scan in the 7- to 15-micron wavelength using a 0.5-meter infrared telescope across a 5.5 by 2-deg. field of view. The IR array will consist of 16 detectors abd scan a 200-deg., full-angle field of regard."
Key features include:
- Most capable NEO detection system in operation
- 200 degree anti-sun Field of Regard, with a 2×5.5 degree Field of View at any point in time: scans 165 square degrees per hour looking for moving objects
- Precise pointing accuracy to sub-pixel resolution for imaging revisit, using the detector fine steering capability
- Designed for highly autonomous, reliable operation requiring only weekly ground contact
- Designed for 5.5 years of surveying operations. Actively cooled to 40K using a Ball Aerospace two-stage, closed-cycle Stirling-cycle cryocooler
- Ability to follow-up on objects of interest
- "Sentinel". Ball Current Programs. Ball Aerospace. 2013. Retrieved 2013-08-02.
- "The Foundation". B612 Foundation. Retrieved September 13, 2012.
- Norris, Guy (2013-04-09). "Ball Aerospace Ramps Up Sentinel Asteroid Search Mission". Aviation Week. Retrieved 2013-04-11.
- "The Sentinel Mission". B612 Foundation. Retrieved September 13, 2012.
- "Foundation History". B612 Foundation. Retrieved April 15, 2012.
- "Sentinel Factsheet" (PDF). B612 Foundation. Retrieved September 13, 2012.
- Wall, Mike (July 10, 2012). "Private Space Telescope Project Could Boost Asteroid Mining". Space.com. Retrieved September 14, 2012.