In the early 1980s, all United States expendable launch vehicles were planned to be phased out in favor of the Space Shuttle, which would be responsible for all government and commercial launches. Production of Delta, Atlas-Centaur, and Titan 34D had ended. The Challenger disaster of 1986 and the subsequent halt of Shuttle operations changed this policy, and President Ronald Reagan announced in December of that year that the Space Shuttle would no longer launch commercial payloads, and NASA would seek to purchase launches on expendable vehicles for missions that did not require crew or Shuttle support.
McDonnell Douglas, at that time the manufacturer of the Delta family, signed a contract with the U.S. Air Force in 1987 to provide seven Delta IIs. These were intended to launch a series of GPS Block II satellites, which had previously been manifested for the Space Shuttle. The Air Force exercised additional contract options in 1988, expanding this order to 20 vehicles, and NASA purchased its first Delta IIs in 1990 for the launch of three Earth-observing satellites.
The first Delta II launch occurred in 1989, with a Delta 6925 boosting the first GPS Block II satellite into a 20,000 km high orbit.
McDonnell Douglas began Delta IIIdevelopment in the mid-90s as increasing satellite mass required more powerful launch vehicles. Delta III, with its liquid hydrogen second stage and more powerful GEM 46 boosters, could bring twice as much mass as Delta II to geostationary transfer orbit (GTO), but a string of two failures and one partial failure, along with the development of the much more powerful Delta IV, led to the cancellation of Delta III program. The upgraded boosters would still find use on the Delta II, leading to the Delta II Heavy.
On March 28, 2003, the Air Force Space Command began the process for deactivating the Delta II launch facilities and infrastructure at Cape Canaveral once the last of the second-generation GPS satellites were launched. However, in 2008, it instead announced that it wouild transfer all the Delta II facilities and infrastructure to NASA to support the launch of GRAIL in 2011.
The last GPS launch aboard a Delta II, and the final launch from SLC-17A at Cape Canaveral AFB was in 2009. The GRAIL Launch in 2011 marked the last Delta II Heavy launch and the last from Florida. The final five launches would all be from Vandenberg.
On July 16, 2012 NASA selected the Delta II to support the Orbiting Carbon Observatory (2014), Soil Moisture Active Passive/SMAP (2016), Joint Polar Satellite System/JPSS (2017), and ICESat-2 (2018) missions. This marked the final purchase of Delta IIs. OCO-2 was launched on July 2, 2014, SMAP was launched on January 31, 2015 and JPSS was launched on November 18, 2017. All of these launches were, or will be, placed into orbit from Complex 2 at Vandenberg Air Force Base in California.
The Delta II family has launched 155 times. Its only unsuccessful launches have been Koreasat 1 in 1995, and GPS IIR-1 in 1997. The Koreasat 1 launch was a partial failure caused by one booster not separating from the first stage, which resulted in the satellite being placed in a lower than intended orbit. By using reserve fuel, it was able to achieve its proper orbit and operated for 10 years. The GPS IIR-1 was a total loss as the Delta II exploded 13 seconds after launch. The explosion occurred when a damaged SRBcasing ruptured and triggered the vehicle's flight termination system.] No one was injured, and the launch pad itself was not seriously impacted, though several cars were destroyed and a few buildings were damaged.
In 2007, Delta II completed its 75th consecutive successful launch, surpassing the 74 consecutive successful launches of the Ariane 4. With the launch of JPSS-1 in 2017, the Delta II has enjoyed 99 consecutive successful launches, with the last one launching September 15th, 2018. Should this launch be successful, the Delta II would achieve an unprecedented 100 consecutive launch successes.
ICESat-2 (Ice, Cloud, and land Elevation Satellite 2), part of NASA's Earth Observing System, is a planned satellite mission for measuring ice sheet elevation and sea ice freeboard, as well as land topography and vegetation characteristics. ICESat-2 is a planned follow-on to the ICESat mission. It will be launched on 15 September 2018 from Vandenberg Air Force Base in California,into a near-circular, near-polar orbit with an altitude of approximately 496 km (308 mi). It is being designed to operate for three years and will carry enough propellant for seven years.
The sole instrument on ICESat-2 will be the Advanced Topographic Laser Altimeter System (ATLAS), a space-based LIDAR. ATLAS will time the flight of laser photons from the satellite to Earth and back; computer programs will use the travel time from multiple pulses to determine elevation.
The ATLAS laser will emit visible laser pulses at 532 nm wavelength. The laser is being developed and built by Fibertek. As ICESat-2 orbits, the ATLAS will generate six beams arranged in three pairs, with the pairs 3.3 km apart, in order to better determine the surface’s slope and provide more ground coverage. ATLAS will take elevation measurements every 70 cm along the satellite’s ground path.
The laser will fire at a rate of 10 kHz. Each pulse sends out about 20 trillion photons, almost all of which are dispersed or deflected as the pulse travels to Earth’s surface and bounces back to the satellite. About a dozen photons from each pulse return to the instrument and are collected in a beryllium telescope.
The National Snow and Ice Data Center Distributed Active Archive Center will manage ICESat-2 science data.[
Today’s #ICESat2 launch comes with a bonus — a pair of tiny satellites that will study how energetic electrons make their way into our atmosphere from space. Meet the twin ELFIN CubeSats hitching a ride to orbit: https://t.co/QT9F69LREN https://t.co/CWLN0GnR6D