ULA’s Delta II launches with THEMIS

by Chris Bergin

A United Launch Alliance (ULA) Delta II has launched with five NASA probes for the THEMIS project from Cape Canaveral Air Force Station this evening, lifting off from Pad 17B at 18:01 local time (23:01 UK time). All five probes successfully seperated some 75 minutes after launch.

NASASpaceflight.com provided extensive live coverage of the event, with background, live updates, comprehensive background on the links below (read more), with a free launch video now available.

**DELTA II/THEMIS – Live Update and Launch Coverage**

**Free launch video** – Free to all forum members (registration is free – we do not use your e-mail for spam, only to send you your forum password – which is automated). A super high quality video is available on L2 now.


Friday’s attempt was coming out of the 10 minute hold prior to the start of T-4 minutes and counting, but a weather balloon came back with data that showed the higher level winds over the range were a constraint to launch.

The 126 foot tall Delta II 7925-10 three-stage launch vehicle will be utilizing six Alliant Techsystems ground start solid motors, with three additional solids being air lit. The first stage core of the Delta II is powered by a Pratt & Whitney Rocketdyne RS-27A main engine operates on liquid oxygen and kerosene (RP-1).

An Aerojet AJ10-118K engine powers the second stage and burns Aerozine-50 fuel with nitrogen tetroxide oxidizer. The third stage is powered by a Thiokol’s Star 48B solid-propellant stage. THEMIS is contained with a 10 foot diameter payload fairing.

THEMIS (Time History of Events and Macroscale Interactions during Substorms) comprises of five identical satellites, which will work together to impartially distinguish between two disparate phenomenological and plasma-physical models of substorm onset in order to solve the mystery of where and when substorms start in the Earth’s magnetosphere.

THEMIS’ five identical spacecraft with identical instruments will line up along the sun-Earth line and track the flow of energy from its point of explosive generation in space into the aurora.

After their release from the launch vehicle, the ground controllers will use the spacecraft’s own propulsion systems to place them in ‘resonant’ highly elliptical orbits, with periods one, two and four days. Every four days the spacecraft will align at distances ranging from 1/6 to 1/2 the way to the moon.

This enables the spacecraft to track the flow of particles and the progression of space currents from one point to another, and identify the elusive substorm point of origin.

The THEMIS program is a NASA Medium Class Explorer (MIDEX) Mission. The program was selected in March 2003 with Swales the Prime Contractor for the Probe Bus and Probe Carrier.

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