Planck (spacecraft)
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| General information | |
|---|---|
| NSSDC ID | 2009-026B |
| Organization | European Space Agency with Thales Alenia Space as Prime Contractorship |
| Launch date | 2009-05-14 13:12:02 UTC |
| Launched from | Guiana Space Centre French Guiana |
| Launch vehicle | Ariane 5 ECA |
| Mission length | elapsed: 1 month and 26 days |
| Location | 1.5 million km (L2 Lagrangian point) |
| Wavelength | 350 to 10,000 µm |
| Instruments | |
| Low Frequency Instrument (LFI) | 30–70 GHz receivers |
| High Frequency Instrument (HFI) | 100–857 GHz receivers |
| Website | Planck Science Team Home |
Planck is a space observatory designed to observe the anisotropies of the cosmic microwave background (CMB) over the entire sky, using high sensitivity and angular resolution. Planck was built in the Cannes Mandelieu Space Center by Thales Alenia Space and created as the third Medium-Sized Mission (M3) of the European Space Agency's Horizon 2000 Scientific Programme. The project—initially called COBRAS/SAMBA after its approval—is named in honour of the German scientist Max Planck (1858–1947), who won the Nobel Prize for Physics in 1918.
The mission will complement and improve upon observations made by the NASA Wilkinson Microwave Anisotropy Probe, which has measured the anisotropies at larger angular scales and lower sensitivity than Planck. Planck will provide a major source of information relevant to several cosmological and astrophysical issues, such as testing theories of the early universe and the origin of cosmic structure.
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[edit] Objectives
The mission has a wide variety of scientific aims, including:[1]
- High resolution detections of both the total intensity and polarization of the primordial CMB anisotropies
- Creation of a catalogue of galaxy clusters through the Sunyaev-Zel'dovich effect
- Observations of the gravitational lensing of the CMB, as well as the integrated Sachs–Wolfe effect
- Observations of bright extragalactic radio (active galactic nuclei) and infrared (dusty galaxy) sources
- Observations of the Milky Way, including the local interstellar medium, distributed synchrotron emission and measurements of the galactic magnetic field.
- Studies of the local Solar System, including planets, asteroids, comets and the zodiacal light.
Planck represents an advance over WMAP in several respects.
- It has higher resolution, allowing it to probe the power spectrum of the CMB to much smaller scales (x3).
- It has higher sensitivity (x10).
- It observes in nine passbands rather than five with the goal of improving the astrophysical foreground models.
It is expected that most Planck measurements will be limited by how well foregrounds can be subtracted, rather than by the detector performance or length of the mission. This is particularly important for the polarization measurements. The dominant foreground depends on frequency, but examples include synchrotron radiation from the Milky Way at low frequencies, and dust at high frequencies.
[edit] Instruments
The spacecraft carries two instruments; the Low Frequency Instrument (LFI) and the High Frequency Instrument (HFI).[1] Both instruments can detect both the total intensity and polarization of photons, and together cover a frequency range of 30 to 857 GHz. The cosmic microwave background spectrum peaks at a frequency of 160.2 GHz
[edit] Low Frequency Instrument
| Frequency (GHz) |
Bandwidth (Δν / ν) |
Resolution (arcmin) |
Sensitivity (total intensity) ΔT / T, 14 month observation (10−6) |
Sensitivity (polarization) ΔT / T, 14 month observation (10−6) |
|---|---|---|---|---|
| 30 | 0.2 | 33 | 2.0 | 2.8 |
| 44 | 0.2 | 24 | 2.7 | 3.9 |
| 70 | 0.2 | 14 | 4.7 | 6.7 |
The LFI has three frequency bands, covering the range of 30–70 GHz. The detectors use High Electron Mobility Transistors.[1]
[edit] High Frequency Instrument
| Frequency (GHz) |
Bandwidth (Δν / ν) |
Resolution (arcmin) |
Sensitivity (total intensity) ΔT / T, 14 month observation (10−6) |
Sensitivity (polarization) ΔT / T, 14 month observation (10−6) |
|---|---|---|---|---|
| 100 | 0.33 | 10 | 2.5 | 4.0 |
| 143 | 0.33 | 7.1 | 2.2 | 4.2 |
| 217 | 0.33 | 5.5 | 4.8 | 9.8 |
| 353 | 0.33 | 5.0 | 14.7 | 29.8 |
| 545 | 0.33 | 5.0 | 147 | N/A |
| 857 | 0.33 | 5.0 | 6700 | N/A |
The HFI has six frequency bands, between 100 and 857 GHz. They use bolometers to detect photons. The four lower frequency bands have sensitivity to linear polarization; the two higher bands do not.[1]
[edit] Service Module – a common development for Herschel and Planck
A common service module (SVM) was designed and built by Thales Alenia Space in its Turin plant, for the Herschel and Planck missions combined into one single program[1] .
Structurally the Herschel and Planck SVM's are very similar. Both SVM's are of octagonal shape and for both, each panel is dedicated to accommodate a designated set of warm units, while taking into account the dissipation requirements of the different warm units, of the instruments as well as the spacecraft.
Furthermore, on both spacecraft a common design for the avionics, the attitude control and measurement system (ACMS) and the command and data management system (CDMS), and power subsystem and the tracking, telemetry and command subsystem (TT&C) has been achieved.
All spacecraft units on the SVM are redundant.
[edit] Power Subsystem
On each spacecraft, the power subsystem consists of the solar array, employing triple-junction solar cells, a battery and the power control unit (PCU). It is designed to interface with the 30 sections of each solar array, provide a regulated 28 V bus, distribute this power via protected outputs and to handle the battery charging and discharging.
For Planck, the circular solar array is fixed on the bottom part of the satellite, facing always the sun, as the satellite is spinning around its vertical axis.
[edit] Attitude and Orbit Control
This function is performed by the attitude control computer (ACC) which is the platform for the ACMS. It is designed to fulfil the pointing and slewing requirements of the Herschel and Planck payload.
The Planck satellite is spun at one revolution per minute, the absolute pointing error needs to be less than 37 arc min. For Planck being a survey platform, there is also a requirement to be met on pointing reproducibility error to be less than 2.5 arc min over 20 days.
The main sensor of the line of sight in both spacecraft is the star tracker.
[edit] Launch and orbit
The satellite was successfully launched, along with the Herschel Space Observatory, at 13:12:02 on 14 May 2009 aboard an Ariane 5 ECA heavy launch vehicle. The launch placed the craft into a very elliptical orbit (perigee: 270 km, apogee: more than 1,120,000 km), bringing it near the L2 Lagrangian point of the Earth-Sun system, 1.5 million kilometers from the Earth.
The maneuver to inject Planck into its final orbit around L2 was successfully completed on July 3, 2009, when it entered a Lissajous orbit of 400,000 km radius around the L2 Lagrangian point.[2] The temperature of the High Frequency Instrument reached just a tenth of a degree above absolute zero (0.1 K) on July 3, 2009, placing both the Low Frequency and High Frequency Instruments within their cryogenic operational parameters, making Planck fully operational.[3]
[edit] See also
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Wikinews has related news: ESA launches Herschel Space Observatory and Planck Satellite |
[edit] References
- ^ a b c d e Planck Science Team (2005) (.PDF). Planck: The Scientific Programme (Blue Book). ESA-SCI (2005)-1. Version 2. European Space Agency. http://www.rssd.esa.int/SA/PLANCK/docs/Bluebook-ESA-SCI%282005%291_V2.pdf. Retrieved on 2009-03-06.
- ^ "Esa, latest news". European Space Agency. http://www.rssd.esa.int/index.php?project=PLANCK&page=dev_news.
- ^ "Planck instruments reach their coldest temperature". European Space Agency. http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=45133.
[edit] Further reading
- Thorsten Dambeck in Sky and Telescope, Planck Readies to Dissect the Big Bang, May 2009, pp. 24–28
[edit] External links
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