 Artist rendering of the Sentinel Space Telescope | |
| Mission type | Space Telescope |
|---|---|
| Operator | B612 Foundation |
| Website | SentinelMission.org at theWayback Machine (archived 8 October 2015) |
| Mission duration | ≤10 years (planned) |
| Spacecraft properties | |
| Manufacturer | Ball Aerospace |
| Launch mass | 1,500 kg (3,300 lb) |
| Start of mission | |
| Launch date | Cancelled |
| Rocket | Falcon 9 |
| Orbital parameters | |
| Reference system | Heliocentric |
| Main | |
| Wavelengths | 7–15 μm |
| Instruments | |
| IRAC IRS | |
TheSentinel Space Telescope was[1] aspace observatory to be developed byBall Aerospace & Technologies for theB612 Foundation.[2][3] The B612 Foundation is dedicated to protecting theEarth from dangerousasteroid strikes and Sentinel was to be the Foundation's first spacecraft tangibly to address that mission.
The space telescope was intended to locate and catalog 90% of the asteroids greater than 140 metres (460 ft) in diameter that exist innear-Earth orbits. The telescope would have orbited the Sun in aVenus-like orbit (i.e. between Earth and theSun). This orbit would allow it clearly to view the night half of the sky every 20 days, and pick out objects that are often difficult, if not impossible, to see in advance from Earth."[4] Sentinel would have had an operational mission life of six and a half to ten years.[5]
AfterNASA terminated their funding agreement with the B612 Foundation in October 2015[6] and the private fundraising goals could not be met, the Foundation eventually opted for an alternative approach using a constellation of much smaller spacecraft under study as of June 2017[update].[1] NASA/JPL'sNEOCam has been proposed instead.
The B612 project grew out of a one-day workshop onasteroid deflection organized byPiet Hut andEd Lu atNASA Johnson Space Center,Houston,Texas on October 20, 2001. ParticipantsRusty Schweickart,Clark Chapman,Piet Hut, andEd Lu established the B612 Foundation on October 7, 2002.[7] The Foundation originally planned to launch Sentinel by December 2016 and to begin data retrieval no later than 6 months after successful positioning.[8]In April 2013, the plan had moved out to launching on aSpaceXFalcon 9 in 2018, followingpreliminary design review in 2014, andcritical design review in 2015.[4]
As of April 2013[update], B612 was attempting to raise approximately $450 million in total to fund the total development and launch cost of Sentinel, at a rate of some $30 to $40 million per year.[4] That funding profile excludes the advertised 2018 launch date.
AfterNASA terminated their $30 million funding agreement with the B612 Foundation in October 2015[6] and the private fundraising did not achieve its goals, the Foundation eventually opted for an alternative approach using a constellation of much smaller spacecraft which is under study as of June 2017[update].[1] NASA/JPL'sNEOCam has been proposed instead.
Unlike similar projects to search fornear-Earth asteroids or near-Earth objects (NEOs) such asNASA'sNear-Earth Object Program, Sentinel would have orbited between Earth and the Sun. Since the Sun would therefore always have been behind the lens of the telescope, it would have never inhibited the telescope's ability to detect NEOs and Sentinel would have been able to perform continuous observation and analysis.
Sentinel was anticipated to be capable of detecting 90% of theasteroids greater than 140 meters in diameter that exist in Earth's orbit, which poseexistential risk to humanity. The B612 Foundation estimates that approximately half a million asteroids in Earth's neighbourhood equal or exceed the one thatstruck Tunguska in 1908.[5] It was planned to be launched atop theFalcon 9 rocket designed and manufactured by theprivate aerospace companySpaceX in 2019,[9] and to be maneuvered into position with the help ofthe gravity of Venus. Data gathered by the Sentinel Project would have been provided through an existing network of scientific data-sharing that includesNASA and academic institutions such as theMinor Planet Center inCambridge, Massachusetts.
Given the satellite's telescopic accuracy, Sentinel's data was speculated to prove valuable for future missions in such fields asasteroid mining.[5][10]
The telescope was intended to measure 7.7 metres (25 ft) by 3.2 metres (10 ft) with a mass of 1,500 kilograms (3,300 lb) and would have orbited 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 in the same orbital distance asVenus. It would have employedinfrared astronomy methods to identify asteroids against thecold ofouter space. TheB612 Foundation worked in partnership withBall Aerospace to construct Sentinel's 0.51 m (20 inches)aluminum mirror, which would have captured the large field of view.[3]"Sentinel will scan in the 7- to 15-micronwavelength using a 0.5-meterinfrared telescope across a 5.5 by 2-deg. field of view. The [infrared] IR array would have consisted of 16 detectors, and coverage would have scanned a 200-degree, full-anglefield of regard."[4]
Key features included:[citation needed]
REP. STEWART: ... are we technologically capable of launching something that could intercept [an asteroid]? ... DR. A'HEARN: No. If we had spacecraft plans on the books already, that would take a year ... I mean a typical small mission ... takes four years from approval to start to launch ...
— Rep. Chris Stewart (R,UT) andDr. Michael F. A'Hearn, 10 April 2013,United States Congress[11]
