The Half-Astrophysicist Blog

Two Satellites, One Rocket

Tomorrow is a big day for the European Space Agency as they launch two big missions on one Ariane 5 rocket.  These are both important missions so there is a lot riding on a successful launch tomorrow.

The first mission is the Hershel Space Observatory.  Herschel is a 3.5 meter space telescope, the largest ever launched (Hubble is a 2.4 meter telescope for reference).  Herschel is not a competitor to the more famous Hubble…Herschel will observe in the far infrared (Hubble does some near infared observations).  The universe looks very different in the infared.  Many cool objects give off most of their light in the infrared. Distant objects.  Herschel will probe the earlierst star forming regions and be able to detect where planets may currently be forming with unprecedented resolution.

To observe in the infared, you need to cool the detectors down to near absolute zero.  Herschel will carry a couple thousand liters of liquid helium to coolits instruments.  Herschel has a large sunshade (as you can see in the diagram) and will obrit the Sun, away from the heat of the Earth (at a point called L2 for those into orbits).  Unfortunately, this limits its lifetime.  It should last at least three years, but then it will warm up.  We cannot service a satellite orbiting at L2, so the mission will be over.  There is a nice mission overview brochure on their website.

The second mission is the Planck satellite.  Planck will make the most detailed observations ever of the cosmic microwave background (CMB) radiation.  The CMB is left over from the big bang.  A previous satellite called WMAP put a lot of of constraints on the age and makeup of the universe by measuring the CMB, but left some major questions unanswered.  Placnk could shed more light on the nature of dark matter, dark energy, and the early history of the universe.

Planck has a couple of things in common with Herschel.  First, it will orbit at L2 (don’t worry, there’s a lot of room out there so they won’t collide!)  Second, it will carry liquid helium to cool its instruments close to absolute zero to make its observations.  Planck is scheduled for 15 months of observationsl, but you can bet they will run it until the last drop of coolant runs out.

This is a big launch with much higher stakes than usual.  You can watch the streaming video here.  Laucnh is scheduled for 9:12am EDT if I am subtracting correctly…good luck Planck and Herschel!


May 14, 2009 - Posted by | Astronomy, ESA

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