May 5, 2009
Two missions to study the cosmos, the Herschel and Planck spacecraft, are scheduled to blast into space May 14 aboard the same Ariane 5 rocket from the Guiana Space Center in French Guiana. The European Space Agency (ESA) leads both missions with significant participation from NASA.
"The missions are quite different, but they'll hitch a ride to space together," said Ulf Israelsson, NASA project manager for both Herschel and Planck. "Launch processing is moving along smoothly. Both missions' instruments have completed their final checkouts, and the spacecrafts' thruster tanks have been fueled."
The Herschel observatory has the unique ability to peek into the dustiest and earliest stages of planet, star, and galaxy growth. The spacecraft's astronomy mirror - about 11.5 feet (3.5 meters) in diameter - is the largest ever launched into space. The mirror will collect longer wavelength light in the infrared and submillimeter range - light never before investigated by an astronomy mission.
"We haven't had ready access to the wavelengths between infrared and microwaves before, in part because Earth's atmosphere blocks them from reaching the ground," said Paul Goldsmith, the project scientist for Herschel at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California. "Because our views were so limited before, we can expect a vast range of serendipitous discoveries, from new molecules in interstellar space to new types of objects."
The coolest objects in the universe, such as dusty, developing stars and galaxies, appear as dark blobs when viewed with visible-light telescopes. As a result, astronomers don't know what happens inside them. However, at longer wavelengths in the far-infrared and submillimeter range, cool objects shine brightly. Herschel will detect light from objects as cold as -441° Fahrenheit (-263° Celsius), which is 10° above the coldest temperature theoretically attainable. Onboard liquid helium, which is expected to last more than 3.5 years, will chill one of Herschel's detectors to a frosty -459° Fahrenheit (-273° Celsius).
Planck will answer fundamental questions about how the universe came to be and how it will change in the future. It will look back in time to just 400,000 years after our universe came into existence nearly 14 billion years ago in the event known as the Big Bang. The mission will spend at least 15 months making the most precise measurements of light at microwave wavelengths across our entire sky, including the cosmic microwave background. This light is from the primordial soup of particles that eventually evolved to become our modern-day universe. The light has traveled about 14 billion years to reach us, and it has cooled and stretched to longer wavelengths because space is expanding.
"The cosmic microwave background shows us the universe directly at age 400,000 years, not the movie, not the historical novel, but the original photons," said Charles Lawrence, project scientist for Planck at NASA's JPL. "Planck will give us the clearest view ever of this baby universe, showing us the results of physical processes in the first brief moments after the Big Bang, and the starting point for the formation of stars and galaxies."
Planck will be cold too. One of its instruments also will be cooled to -459° Fahrenheit (-273 Celsius). Innovative "cryocooler" technology, developed in part by JPL, will chill the instruments.
Shortly after launch, Planck and Herschel will separate from the rocket and follow different trajectories to the second Lagrangian point of our solar system, a point in space 930,000 miles (1.5 million kilometers) from Earth.