Cosmic time machine set for launch into space Thursday
BY STEPHEN CLARK
Posted: May 13, 2009
Europe is planning to launch a sharp-eyed observatory Thursday to give humans their furthest look back in time to see the cosmic fingerprint of the Big Bang.
"Cosmology is the science that deals with the structure and the contents of the universe," said Jan Tauber, the mission's project scientist at the European Space Agency. "Planck is quite important for (everyone) who is interested in the universe that we live in."
The Planck observatory will observe the cosmic microwave background radiation left over about 380,000 years after the Big Bang. The CMB is considered the first light from the young universe after matter and light could exist independently as the universe cooled.
"Planck is going to take a picture of the universe when it was very young," Tauber said.
Scientists estimate the universe is about 13.7 billion years old and formed when a compressed ball of hot matter exploded outward in an unimaginably intense event called the Big Bang.
"It's like looking at the first day in the life of a human being," Tauber said.
The 4,235-pound spacecraft stands 13.8 feet tall and also has a diameter of about 13.8 feet. It was built by an industrial consortium led by Thales Alenia Space of France.
The mission was named for Max Planck, a German physicist that established the quantum theory, which revolutioned scientists' understanding of atomic and subatomic processes.
Liftoff is set for 1312 GMT (9:12 a.m. EDT) Thursday aboard a commercial Ariane 5 rocket launched from Kourou, French Guiana.
Planck will share the Ariane 5 launch with Herschel, the world's most advanced infrared telescope designed to help scientists learn more about star formation and the evolution of galaxies.
Herschel will first separate from the Ariane 5, followed by the deployment of Planck about 28 minutes after launch.
The Ariane 5 is boosting the spacecraft into an unusually high orbit stretching to an altitude of more than 700,000 miles. Both payloads are bound to the second Lagrange point nearly 1 million miles from the night side of Earth, four times past the orbit of the moon.
The L2 point is a popular destination for astronomy missions because it was far enough away from Earth to rid the observatories of interfering radiation, but close enough to allow regular high-band communications with ground stations.
"We can turn our back to the sun, the Earth and the moon and point the satellite into deep space so it cools down very effectively," Tauber said.
L2 is the point where the tug of gravity from the Earth and sun balance, allowing spacecraft stationed there to stay in lockstep with the planet as it circles the sun.
"There are a lot of advantages of being at L2. It just takes a big rocket to get you there, but we have one so that's OK," Tauber said.
Planck will reach L2 about two months after launch and enter a looping orbit around the point with an average amplitude of about 250,000 miles.
The spacecraft's thrusters will be fired to put it on a different trajectory from Herschel, which is headed for a larger orbit around L2.
Engineers will immediately begin testing Planck's systems after separating from the launcher, but science operations can't begin until the probe arrives at L2, according to Thomas Passvogel, ESA's project manager for the Herschel and Planck missions.
It will take 50 days for pressurized helium aboard Planck to cool down the observatory's detectors enough to begin observations, Passvogel said.
Planck's Low Frequency Instrument must be chilled to 20 Kelvin, or about -424 degrees Fahrenheit.
The helium must cool Planck's High Frequency Instrument to one-tenth of a degree above absolute zero, the coldest temperature physically possible.
NASA's Jet Propulsion Laboratory provided part of Planck's cooling system, amplifier technology for the LFI unit, and critical detectors for the HFI payload.
U.S. and Canadian researchers are also part of the Planck science team.
The agency's investment in Planck totals about $117 million, according to a NASA spokesperson.
The instruments must be cold enough to sense warmth from the cosmic microwave background in the furthest reaches of the universe, which averages about 2.7 Kelvin, or -455 degrees Fahrenheit.
LFI's science team is led by researchers in Italy and HFI was provided by scientists led French principal investigators.
"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, Planck project scientist at NASA.
Warm sensors would be swamped by hot nearby objects, washing out the cold radiation left over from the Big Bang, according to Tauber.
Planck will measure subtle differences in the CMB across the entire sky.
"The signals we are trying to detect are variations about a millionth of the average (CMB) temperature," Tauber said.
Officials say Planck will measure the CMB up to the limits of fundamental astrophysics, obtaining as much information as can possibly be learned by studying the primordial radiation, according to ESA.
"Planck is certainly pushing the boundaries," Tauber said.
"Planck is trying to measure a signal that would be comparable to measuring from Earth the natural heat emission of a small animal like a rabbit that would be placed on the moon," Tauber said.
Although Planck will be gathering incoming light at very low temperatures, the CMB had a temperature of nearly 5,000 degrees Fahrenheit when the light was emitted.
The energy cooled and stretched to longer wavelengths over time because the universe is expanding, according to scientists.
Planck will collect the light through a mirror with a diameter of 1.5 meters, or about 5 feet.
Scientists must analyze the images to remove microwave sources within the Milky Way to get a clear picture of the CMB, according to Tauber.
The observatory will map the CMB with higher fidelity than its two predecessors, NASA's COBE and WMAP missions.
"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, galaxies and clusters of galaxies," Lawrence said.
Launched in 1989, COBE mapped variations in CMB across the whole sky and earned a Nobel Prize for Physics for two of the mission's scientists.
WMAP began observing the CMB in 2001 to create a more detailed map. The probe is still operating and returning data.
Planck will fill in the rest of the CMB picture. And there is a lot left to learn, Tauber said.
"We still have about 15 times more information that we can extract in respect to WMAP," Tauber said.
Planck's instruments also cover a frequency range 10 times larger than WMAP.
But WMAP is no slouch.
Scientists extrapolated data from WMAP to pin down the age of the universe to 13.73 billion years, accurate to within about 120 million years.
WMAP found that dark matter, material not made of atoms, makes up about 23.3 percent of the universe. WMAP also confirmed the existence of dark energy as 72.1 percent of the universe, causing its expansion to speed up.
"The Planck High Frequency Instrument has a raw sensitivity advantage, so Planck should significantly improve upon WMAP," said Chuck Bennett, WMAP's principal investigator. "We are expecting great things out of the Planck mission."
Planck will build on the legacy of WMAP by helping scientists improve their understanding of dark energy and test the cosmology inflation theory, which states that the universe underwent a rapid, exponential expansion a fraction of a second after the Big Bang.
"In some ways, Planck is a follow-on to other missions and will complete what they have done," Tauber said. "But it will also yield a lot of new information in other areas, and possibly even big discoveries."
The observatory could confirm inflation occurred if it can detect B-modes, a type of signal polarization scientists think was caused by ancient gravity from clumps of mass in the early universe.
"That's considered a very big thing in cosmology nowadays, and I think Planck is the mission that has a chance to detect that," Tauber said.
Confirmation of the inflation theory would mean scientists would have their first insight into the initial second of the history of the universe, which would be a substantial discovery unlike anything before in cosmology.
Officials expect Planck will begin scanning the sky about three months after launch. Plans call for the observatory to complete at least two all-sky maps by the end of the mission, which is currently expected around the end of 2010.
It may be three or four years before the Planck team is ready to present the mission's results, Tauber said.
Scientists are waiting to see what Planck learns before proposing another mission dedicated to observing the CMB.
"We first have to see what Planck does, and then the picture will be far clearer to see if it's worth trying to design a new mission," Tauber said.
Planck was first studied by ESA in 1994, beginning a 15-year journey from the drawing board to the launch pad.
That wait will be over Thursday, but it will be just the start of a new voyage back in time for cosmologists and science buffs.
"Now we just have to wait on the results, but they will be amazing," Passvogel said.