Planck is ESA’s first mission to study CMBR (Cosmic Microwave Background Radiation), the oldest observable light of the big bang. It was formerly known as COBRAS/SAMBA and was selected for ESA’s Horizon 2000 Specific Programme in 1996. The mission is expected to bring about answers to the most perplexing questions in modern cosmology, for example, age and fate of the universe, the nature of dark matter and dark energy. One of the most distinguishing features of the Planck mission is its cooling system. The satellite employs a three-stage active cryogenic cooler. The last cooling stage makes use of the cooling effect of mixing two isotopes of helium. This cools the satellite to about -273oC (few tenths of a degree above absolute zero) which is a significant improvement from Spitzer’s -271 oC temperatures, which used liquid helium and has now run out.
Left bottom: The Planck cooling system. Image: ESA
Right-Bottom: Planck satellite in foreground of CMBR radiation diagram. Credits: ESA
The fundamental objectives that the Planck data is expected to achieve are:
1. Determining fundamental characteristics of the universe like density, geometry etc.
2. Accurate measurement of fluctuations in CMBR.
3. Detect existence of cosmic strings.
4. Provide information about the inflation period just after big bang.
Right: Planck satellite at cleaning. Image: ESA
Right: Planck Qualification model. Image: ESA
1. Name: Planck
2. Launch Date: 14th May, 2009
3. Launch Site: Kourou, French Guiana
4. Launch Vehicle: Ariane 5
5. Cost: 700 million euros including launch, payload and operations
6. Mass: 1950 Kg at launch.
7. Dimension: 4.2 m height with a maximum diameter of 4.2 m.
8. Programme Manager: Thomas Passvogel
9. Project Scientist: Jan Tauber
10. Primary Ground Station: ESA’s deep space antenna in New Norcia, Australia.
11. Lifetime: 15 months + possible 1 year extension.
12. Wavelength**:** Microwave: 27 GHz to 1 Thz
13. Orbit: A Lissajous orbit about Langrangian point 2 or L2 of Sun-Earth system with an average amplitude of 400,000 Km about L2. These orbits are quasiperiodic. The orbit was chosen to avoid solar radiation as well as Earth’s thermal radiation.
The Planck satellite has two instruments as its payloads:
1. Low Frequency Instrument (LFI): The LFI is designed to produce high-sensitivity, multi-frequency measurements of the microwave sky in the frequency range 27 to 77 GHz (wavelength range 11.1 to 3.9 mm).
2. The High Frequency Instrument (HFI): The HFI is designed to produce high-sensitivity, multi-frequency measurements of the diffuse sky radiation in the frequency range 84 GHz to 1 THz (wavelength range 3.6 to 0.3 mm). This instrument is successively cooled by three different mechanisms - Hydrogen absorption, Joule-Thompson and Helium dilution.
Both these payloads share a common telescope with a 1.9 x 1.5 m primary and a 1.1 x 1.0 m secondary paraboloid mirror.