B. Mot

PILOT: a balloon-borne experiment to measure the polarized FIR emission of dust grains in the interstellar medium

Future cosmology space missions will concentrate on measuring the polarization of the Cosmic Microwave Back- ground, which potentially carries invaluable information about the earliest phases of the evolution of our universe. Such ambitious projects will ultimately be limited by the sensitivity of the instrument and by the accuracy at which polarized foreground emission from our own Galaxy can be subtracted out. We present the PILOT balloon project which will aim at characterizing one of these foreground sources, the polarization of the dust continuum emission in the diffuse interstellar medium. The PILOT experiment will also constitute a test-bed for using multiplexed bolometer arrays for polarization measurements. We present the results of ground tests obtained just before the first flight of the instrument.

Current design of the electrical architecture for the payload module of LiteBIRD

LiteBIRD is a space-borne project for mapping the anisotropy of the linear polarization of the cosmic microwave background (CMB). The project aims to measure the B-mode pattern in a large angular scale to test the cosmic inflation theory. It is currently in the design phase lead by an international team of Japan, US, Canada, and Europe. We report the current status of the design of the electrical architecture of the payload module of the satellite, which is based on the heritages of other cryogenic space science missions using bolometers or microcalorimeters.

PILOT: optical performance and end-to-end characterisation

PILOT (Polarized Instrument for the Long-wavelength Observations of the Tenuous ISM), is a balloon-borne astronomy experiment dedicated to study the polarization of dust emission from the diffuse ISM in our Galaxy [1]. The observations of PILOT have two major scientific objectives. Firstly, they will allow us to constrain the large-scale geometry of the magnetic field in our Galaxy and to study in details the alignment properties of dust grains with respect to the magnetic field. In this domain, the measurements of PILOT will complement those of the Planck satellite at longer wavelengths. In particular, they will bring information at a better angular resolution, which is critical in crowded regions such as the Galactic plane. They will allow us to better understand how the magnetic field is shaping the ISM material on large scale in molecular clouds, and the role it plays in the gravitational collapse leading to star formation. Secondly, the PILOT observations will allow us to measure for the first time the polarized dust emission towards the most diffuse regions of the sky, where the measurements are the most easily interpreted in terms of the physics of dust. In this particular domain, PILOT will play a role for future CMB missions similar to that played by the Archeops experiment for Planck. The results of PILOT will allow us to gain knowledge about the magnetic properties of dust grains and about the structure of the magnetic field in the diffuse ISM that is necessary to a precise foreground subtraction in future polarized CMB measurements. The PILOT measurements, combined with those of Planck at longer wavelengths, will therefore allow us to further constrain the dust models. The outcome of such studies will likely impact the instrumental and technical choices for the future space missions dedicated to CMB polarization. The PILOT instrument will allow observations in two photometric channels at wavelengths 240 μm and 550 μm, with an angular resolution of a few arcminutes. We will make use of large format bolometer arrays, developed for the PACS instrument on board the Herschel satellite. With 1024 detectors per photometric channel and photometric band optimized for the measurement of dust emission, PILOT is likely to become the most sensitive experiment for this type of measurements. The PILOT experiment will take advantage of the large gain in sensitivity allowed by the use of large format, filled bolometer arrays at frequencies more favorable to the detection of dust emission. This paper presents the optical design, optical characterization and its performance. We begin with a presentation of the instrument and the optical system and then we summarise the main optical tests performed. In section III, we present preliminary end-to-end test results.

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.

Pilot, a balloon borne experiment underground tests

PILOT is a balloon borne experiment, which will measure the polarized emission of dust grains, in the interstellar medium, in the sub millimeter range (with two photometric channels centered at 240 and 550 μm). The primary and secondary mirror must be positioned with accuracies better than 0.6 mm and 0.06°. These tolerances include environmental conditions (mainly gravity and thermo-elastic effects), uncertainties on alignments, and uncertainties on the dilatation coefficient. In order to respect these tolerances, we need precise characterization of each optical component. The characterization of the primary mirror and the integrated instrument is performed using a dedicated submillimeter test bench. A brief description of the scientific objectives and instrumental concept is given in the first part. We present, in the second and in the third part, the status of these ground tests, first results and planned tests.

Inflight performance of the PILOT balloon-borne experiment

PILOT is a stratospheric experiment designed to measure the polarization of dust FIR emission, towards the diffuse interstellar medium. The first PILOT flight was carried out from Timmins in Ontario-Canada on September 20th 2015. The flight has been part of a launch campaign operated by the CNES, which has allowed to launch 4 experiments, including PILOT. The purpose of this paper is to describe the performance of the instrument in flight and to perform a first comparison with those achieved during ground tests. The analysis of the flight data is on-going, in particular the identification of instrumental systematic effects, the minimization of their impact and the quantification of their remaining effect on the polarization data. At the end of this paper, we shortly illustrate the quality of the scientific observations obtained during this first flight, at the current stage of systematic effect removal.

PILOT optical alignment

PILOT is a balloon-borne astronomy experiment designed to study the polarization of dust emission in the diffuse interstellar medium in our Galaxy at wavelengths 240 μm with an angular resolution about two arcminutes. Pilot optics is composed an off-axis Gregorian type telescope and a refractive re-imager system. All optical elements, except the primary mirror, are in a cryostat cooled to 3K. We combined the optical, 3D dimensional measurement methods and thermo-elastic modeling to perform the optical alignment. The talk describes the system analysis, the alignment procedure, and finally the performances obtained during the first flight in September 2015.

Optical Design and Ground Tests, for Pilot, a Balloon Borne Experiment for Astronomy

PILOT is a balloon borne experiment, which will measure the polarized emission of interstellar dust grains, in the submillimeter range. We present the instrumental concept and the associated ground tests in progress and planned.