QUIJOTE CMB Experiment. Brief Description

The QUIJOTE (Q U I JOint TEnerife) CMB Experiment operates from Teide Observatory with the goal of characterizing the polarization of the CMB and other galactic and extragalactic emission in the frequency range 10-40 GHz, and at large angular scales.

The main objective of the QUIJOTE project is to cover a sky area of 5,000 square degrees, with a sensitivity around 1 µK (at the highest frequencies) and an angular resolution of 1° at 11, 13, 17, 19, 30 and 40 GHz. These measurements will complement at low frequency and correct from galactic contamination those to be obtained by the Planck satellite. They will be the most sensitive measurements obtained for characterization of the synchrotron and anomalous microwave emission in our Galaxy at those frequencies.

The project baseline has two phases, fully funded:

The table below summarizes the summarizes the basic (nominal) characteristic of these three instruments in phases I and II.

Table 1. Nominal characteristics of the three QUIJOTE-CMB instruments: MFI, TGI and FGI. Sensitivities are referred to Stokes Q and U parameters. 

  MFI   TGI FGI

Frequency [GHz] 11.0 13.0 17.0 19.0   31.0 41.0
Bandwidth [GHz] 2.0 2.0 2.0 2.0   10.0 12.0
Number of horns 2 2 2 2   31 31
Channels per horn 4 4 4 4   4 4
Tsys [K] 25.0 25.0 25.0 25.0   35.0 45.0
Beam FWHM [deg] 0.92 0.92 0.60 0.60   0.37 0.28
NET [µK s^1/2] 280 280 280 280   50 57
Sensitivity per beam [Jy s^1/2] 0.30 0.42 0.31 0.38   0.06 0.08

 

The QUIJOTE telescopes

The layout of both QT1 and QT2 telescopes is based on an altazimuth mount supporting a primary (parabolic) and a secondary (hyperbolic) mirror disposed in an offset Gregorian Dracon scheme, which provides optimal cross-polarisation properties (designed to be ≤ −35 dB) and symmetric beams. Each primary mirror has a 2.25m projected aperture, while the secondary has 1.89m. The system is under-illuminated to minimize side-lobes and ground spillover. Each telescope is mounted on its own platform that can rotate around the vertical axis at a maximum frequency of 6 rpm (i.e., 36 deg/s). We note that the QT1 mirrors have been designed to operate up to 90GHz (i.e., rms ≤ 20 μm and maximum deviation of d = 100μm). However, QT2 has been specified to have a better surface accuracy, so the telescope could in principle operate up to 200 GHz.

QUIJOTE - First Instrument (II)

 

The Multi-Frequency Instrument (MFI)

The first QUIJOTE Instrument (or Multi-Frequency Instrument) has four horns, two with receivers at 11-13GHz, and two more at 17-19 GHz. Originally, it was designed with an additional receiver at 30 GHz inside a horn at the center of the focal plane, but this horn was later removed. In total, there are 8 channels in each one of the four frequencies 11, 13, 17 and 19GHz, making 32 channels in total. With the MFI, and after one year of operation, we will reach a sensitivity of 4 µK in the low frequency channels (11-19 GHz), covering a sky area between 5,000 and 10,000 square degrees.

QUIJOTE - First Instrument (I)

The QUIJOTE Source Substractor Facility

Originally, we planned to include a dedicated instrument at 30 GHz, which is an upgraded version of the VSA source substractor converted into a polarimeter, will be used to produce a catalogue of polarization measurements at 30 GHz for radiosources with fluxes above 200 mJy in intensity. This information could be used to correct the QUIJOTE maps from the contamination of radiosources. Figure shows the two antennas of the Source Subtractor, already installed at the Teide Observatory (Tenerife, Spain). Finally, this correction of point sources will be done using VLA observations.

QUIJOTE - Source subtractor

 

The Thirty-GHz Instrument (TGI)

The second QUIJOTE Instrument (or 30 GHz Instrument) will be mainly devoted to primordial B-mode science. TGI will be fitted with 31 polarimeters working in the range of 26-36GHz. The current design of a single polarimeter for the TGI is presented in the figure below. It includes a fixed polarizer and 90 deg and 180 deg phase switches to generate four polarisation states to minimize the different
systematics in the receiver.

TGI scheme

 

The Forty-GHz Instrument (FGI)

Also devoted to primordial B-mode science, the third QUIJOTE Instrument (or 40 GHz Instrument) will be fitted with 31 polarimeters working at 40GHz. The conceptual design of a polarimeter chain for the FGI is identical to the one used for the TGI (see figure above). Funding for the FGI is provided by the Consolider-Ingenio project CSD2010-00064 (EPI:Exploring the Physics of Inflation).