
In its final mission, the United Launch Alliance Delta II launch vehicle lifted NASA’s ICESat-2 (Ice, Cloud, and land Elevation Satellite 2) up into orbit. Designed to measure ice sheet elevation and sea ice freeboard, as well as land topography and vegetation characteristics, the mission is a follow-on to the ICESat mission of 2003 to 2010.
The launch vehicle lifted-off from Space Launch Complex 2 at Vandenberg Air Force Base in California at 06:02 local time (9:02 EDT; 14:02 BST). The satellite separated from the second stage about 53 minutes after lift-off, followed by four cubesat secondary payloads some 20 minutes later.
The half-tonne satellite, about the size of a small car, carries a single instrument: a laser altimeter called the Advanced Topographic Laser Altimeter System (ATLAS). It is designed to fire 10,000 laser pulses a second to obtain elevation data with an accuracy of half a centimetre, and will primarily be used to measure the elevation of ice sheets and changes in their size, but will also measure the height of vegetation on land.

Originally, ICESat-2 had been due to launch in 2015 as a follow-up to the original mission. However, the complexity of ATLAS meant that the mission hit delays and overran its original budget, both of which left NASA facing an either / or situation: either divert funds from other Earth resources missions (such as the Pre-Aerosol, Clouds, and Ocean Ecosystem (PACE) satellite) and cancel them, or cancel ICESat-2.
The first ICESat revealed that sea ice was thinning, and ice cover was disappearing from coastal areas in Greenland and Antarctica. Due to the delays in developing and launching ICESat-2, NASA has relied on an aircraft mission, Operation IceBridge, to monitor ice elevation and gathering other data on ice changes in both the Arctic and Antarctic.
While there are those who like to believe human-made global warming doesn’t exist, and that the unprecedented increases in temperature Earth has experienced in the last 100 or so years is simply a matter of solar cycles (a view that actually does not stand up to objective scrutiny), global average temperatures are climbing year after year (four of the hottest years in modern times all taking place from 2014-2017), largely as a result of humanity’s constant reliance on fossil fuels for energy. This warming is contributing to the shrinking ice cover in the Arctic and Greenland and adding to sea level rises that threaten hundreds of millions of people living in coastal regions around the world, as well as contributing to further weather and climate changes.

ICESat-2 should help scientists understand just how much melting the ice sheets are contributing to this sea level rise, with ATLAS being fired-up for the first time in orbit in around a week’s time.
The launch was the 155th and final flight of the Delta II, which first entered service in 1989. Once a mainstay of both government and commercial customers, the vehicle has seen decreasing use in favour of vehicles like the Delta IV and Atlas launchers and, more recently, SpaceX. In 2007, it was announced ULA would phase out the Delta II – although it has enough parts to build around half-a-dozen complete versions of the rocket. With NASA the only user for the vehicle, it has taken time to use these remaining vehicles, and the final vehicle will be used as a museum piece.
The Delta II occupies a unique place in history: it is the only rocket ever to recorded to have debris strike a human. In 1996, the US Ballistic Missile Defense Organisation (BMDO) launched the Midcourse Space Experiment (MSX) atop a Delta II. Ten months later, on January 22nd, 1997, the upper stage of the launcher re-entered the atmosphere and broke apart, the greater part of it burning up in a fireball over the mid-west United States.

Witnessing the fireball while exercising in a park in Tulsa, Oklahoma, was Lottie Williams. Thirty minutes later, she was struck on the shoulder by a charred piece of metal about 15 cm (6 in) across and weighing about the same as an empty soda can. She was uninjured by the strike, and analysis of the object confirmed it originated from the Delta’s upper stage.
Continue reading “Space Sunday: Earth’s ice and Soyuz leaks”

















