Delta II launches with STEREO

by Chris Bergin

A Boeing Delta II (7925-10L) launch vehicle has launched, carrying the STEREO (Solar TErrestrial RElations Observatory) into orbit for NASA. Launch was at 8:52pm EDT from Cape Canaveral Air Force Station in Florida.

The launch was slightly delayed to the end of the 15 minute launch window due to a constraint on the range. A nominal separation occurred around 25 minutes after launch.


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The mission’s Delta II 7925-10L configuration launch vehicle used a Pratt & Whitney Rocketdyne RS-27A main engine, nine ATK solid rocket motors, an Aerojet second stage engine and a 10-foot diameter payload fairing.

‘STEREO is another exciting mission for NASA to help them gain a better understanding of our universe,’ said Dan Collins, vice president and general manager, Boeing Launch Systems.

‘Our Delta team takes tremendous pride in our work, and we are extremely pleased to help NASA reach its goals.’

Mission Preview

The STEREO launch will mark the third mission in NASA’s Solar Terrestrial Probes (STP) program, on a two year mission to observe the sun, dramatically improving the understanding of the powerful solar eruptions that can send more than a billion tons of the sun’s outer atmosphere hurtling into space.

The STEREO mission comprises two nearly identical spacecraft the size of golf carts. Their observations will enable scientists to construct the first-ever three-dimensional views of the sun. These images will show the sun’s stormy environment and its effect on the inner solar system. The data are vital for understanding how the sun creates space weather.

During the two-year mission, the two spacecraft will explore the origin, evolution and interplanetary consequences of coronal mass ejections, some of the most violent explosions in our solar system. When directed at Earth, these billion-ton eruptions can produce spectacular aurora and disrupt satellites, radio communications and power systems. Energetic particles associated with these solar eruptions permeate the entire solar system and may be hazardous to spacecraft and astronauts.

‘In terms of space-weather forecasting, we’re where weather forecasters were in the 1950s,’ said Michael Kaiser, STEREO project scientist at NASA’s Goddard Space Flight Center. ‘They didn’t see hurricanes until the rain clouds were right above them. In our case, we can see storms leaving the sun, but we have to make guesses and use models to figure out if and when they will impact Earth.’

The mission will employ two nearly identical space-based observatories – one ahead of Earth in its orbit, the other trailing behind – to provide the first-ever stereoscopic measurements to study the Sun and the nature of its coronal mass ejections, or CMEs.

The two solar-powered observatories with 3-axis-stabilization, will each have a launch mass (including propellant) of approximately 1,364 pounds (620 kilograms). The spacecraft will communicate with the APL-based (The Johns Hopkins University Applied Physics Laboratory) Mission Operations Center via NASA’s Deep Space Network.

Each STEREO observatory has 16 instruments. The observatories have imaging telescopes and equipment to measure solar wind particles and to perform radio astronomy.

‘STEREO is charting new territory for science research and the building of spacecraft. The simultaneous assembly, integration and launch of nearly identical observatories have been an extraordinary challenge,’ said Nick Chrissotimos, STEREO project manager a Goddard.

Onboard instruments for STEREO include:

Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) will have four instruments: an extreme ultraviolet imager, two white-light coronagraphs and a heliospheric imager. These instruments will study the 3-D evolution of CME’s from birth at the Sun’s surface through the corona and interplanetary medium to its eventual impact at Earth.

STEREO/WAVES (SWAVES) is an interplanetary radio burst tracker that will trace the generation and evolution of traveling radio disturbances from the Sun to the orbit of Earth.

In-situ Measurements of Particles and CME Transients (IMPACT) will sample the 3-D distribution and provide plasma characteristics of solar energetic particles and the local vector magnetic field.

PLAsma and SupraThermal Ion Composition (PLASTIC) will provide plasma characteristics of protons, alpha particles and heavy ions. This experiment will provide key diagnostic measurements of the form of mass and charge state composition of heavy ions and characterize the CME plasma from ambient coronal plasma.

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