J.-P. Torre

The Planck High Frequency Instrument, a third generation CMB experiment, and a full sky submillimeter survey

The High Frequency Instrument (HFI) of Planck is the most sensitive CMB experiment ever planned. Statistical fluctuations (photon noise) of the CMB itself will be the major limitation to the sensitivity of the CMB channels. Higher frequency channels will measure galactic foregrounds. Together with the Low Frequency Instrument, this will make a unique tool to measure the full sky and to separate the various components of its spectrum. Measurement of the polarization of these various components will give a new picture of the CMB. In addition, HFI will provide the scientific community with new full sky maps of intensity and polarization at six frequencies, with unprecedented angular resolution and sensitivity. This paper describes the logics that prevailed to define the HFI and the performances expected from this instrument. It details several features of the HFI design that has not been published up to now.

Planck pre-launch status: HFI ground calibration

Context. The Planck satellite was successfully launched on May 14th 2009. We have completed the pre-launch calibration measurements of the High Frequency Instrument (HFI) on board Planck and their processing. Aims. We present the results ot the pre-launch calibration of HFI in which we have multiple objectives. First, we determine instrumental parameters that cannot be measured in-flight and predict parameters that can. Second, we take the opportunity to operate and understand the instrument under a wide range of anticipated operating conditions. Finally, we estimate the performance of the instrument built. Methods. We obtained our pre-launch calibration results by characterising the component and subsystems, then by calibrating the focal plane at IAS (Orsay) in the Saturne simulator, and later from the tests at the satellite level carried out in the CSL (Liege) cryogenic vacuum chamber. We developed models to estimate the instrument pre-launch parameters when no measurement could be performed. Results. We reliably measure the Planck-HFI instrument characteristics and behaviour, and determine the flight nominal setting of all parameters. The expected in-flight performance exceeds the requirements and is close or superior to the goal specifications.

The Planck high-frequency instrument: a third-generation CMB probe and the first submillimeter surveyor

The High Frequency Instrument of the Planck satellite is dedicated to the measurement of the anisotropy of the Cosmic Microwave Background (CMB). Its main goal is to map the CMB with a sensitivity of ΔT/T=2.10-6 and an angular resolution of 5 arcmin in order to constrain cosmological parameters. Planck is a project of the European Space Agency based on a wide international collaboration, including United States and Canadian laboratories. The architecture of the satellite is driven by the thermal requirements resulting from the search for low photon noise. Especially, the passively cooled telescope should be at less than 50K, while a cascade of cryo-coolers will ensure the cooling of the HFI bolometers down to 0.1K. This last temperature will be produced by a gravity insensitive 3He/4He dilution cooler. This will be achieved at the L2 Lagrangian point of the Sun-Earth system. The whole sky will be observed two times in the 14 months mission with a scanning strategy based on a 1RPM rotation of the satellite. In addition to the cosmological parameters that can be derived from the CMB maps, Planck will deliver nine high sensitivity submillimeter maps of the whole sky that will constitute unique data available to the whole astronomical community.

Use of high sensitivity bolometers for astronomy: Planck high frequency instrument

The Planck satellite is dedicated to the measurement of the anisotropy of the Cosmic Microwave Background (CMB) with unprecedented sensitivity and angular resolution. It is a project of the European Space Agency based on a wide international collaboration, including United States and Canadian laboratories. The detectors of its High Frequency Instrument (HFI) are bolometers cooled down to 100 mK. Their sensitivity will be limited by the photon noise of the CMB itself at low frequencies, and of the instrument background at high frequencies. The requirements on the measurement chain are directly related to the strategy of observation used for the satellite. This impacts the bolometer design as well as other elements: The cooling system must present outstanding temperature stability, and the amplification chain must show a flat noise spectrum down to very low frequencies.

The High Frequency Instrument of Planck: Requirements and Design

The Planck satellite is a project of the European Space Agency based on a wide international collaboration, including United States and Canadian laboratories. It is dedicated to the measurement of the anisotropy of the Cosmic Microwave Background (CMB) with unprecedented sensitivity and angular resolution. The detectors of its High frequency Instrument (HFI) are bolometers cooled down to 100 mK. Their sensitivity will be limited by the photon noise of the CMB itself at low frequencies, and of the instrument background at high frequencies. The requirements on the measurement chain are directly related to the strategy of observation used for the satellite. Due to the scanning on the sky, time features of the measurement chain are directly transformed into angular features in the sky maps. This impacts the bolometer design as well as other elements: For example, the cooling system must present outstanding temperature stability, and the amplification chain must show, down to very low frequencies, a flat noise spectrum.

Pilot optical alignment

PILOT (Polarized Instrument for Long wavelength Observations of the Tenuous interstellar medium) is a balloonborne astronomy experiment designed to study the polarization of dust emission in the diffuse interstellar medium in our Galaxy. The PILOT instrument allows observations at wavelengths 240 μm (1.2THz) with an angular resolution about two arc-minutes. The observations performed during the first flight in September 2015 at Timmins, Ontario Canada, have demonstrated the optical performances of the instrument.

PRONAOS submillimeter observations of the Orion clouds

Submillimeter observations have been performed by the french balloon‐borne experiment PRONAOS, during its first flight in September 1994. The instrument consisted mainly of a two‐meter telescope and a multiband photometer (from 180 to 1100 μm). Despite bad altitude and attitude controls, a map of an extended area (10′×50′) containing the M42 nebula, has been drawn up in the four photometric bands, with angular beams from 2′ to 3.5′. The flux values measured in the four bands, on the brightest source associated to the BN/KL objects, are compatible with a thermal spectrum emitted by dust with an emissivity power law Qemαν1.5. Around this source, three other brightness peaks are observed, two of them coincident with enhancements in the 100 μm IRAS map. The third one is about 5′×5′ in size, and can be interpreted as the dust emission of a very cold (about 10±2 K) molecular cloud. The in‐flight ’’Noise Equivalent Brightness’’ is 1.7 MJysr−1 s1/2 in the longer wavelength band. The pointing stability is better t...

THERMAL SPECTROMETRY OF PARTICLES AND γ-RAYS WITH COOLED COMPOSITE BOLOMETERS OF MASS UP TO 25 GRAMS

The composite bolometer with monolithic doped germanium thermistor is a good approach towards the ideal thermal spectrometer. We have measured the thermal parameters of heavily doped germanium that are required to optimize the thermal coupling between substrate and sensor. Sensors in the megohm range are obtained by high precision resistivity tests and pre-selection at 300K. Heat capacity corresponding to 2 eV resolution has been measured at 40 mK. We have tested with success several bolometers with mass from 1 mg to 25 g. Best FWHM resolutions obtained are 29 KeV on αs, 2 KeV on e − s and 300 eV on γs. These results are obtained by filtering extraneous sources of energy like microphonics. We have reached a resolution of 16 KeV on a γ line with a 25 gram sapphire composite bolometer at 0.1K which is the largest and most massive bolometer ever successfully tested; it confirms the promising possibilities of bolometers for dark matter particles detection.