Euclid preparation. XXIX. Water ice in spacecraft part I: The physics of ice formation and contamination

Abstract

Molecular contamination is a well-known problem in space flight. Water is the most common contaminant and alters numerous properties of a cryogenic optical system. Too much ice means that Euclid's calibration requirements and science goals cannot be met. Euclid must then be thermally decontaminated, a long and risky process. We need to understand how iced optics affect the data and when a decontamination is required. This is essential to build adequate calibration and survey plans, yet a comprehensive analysis in the context of an astrophysical space survey has not been done before. In this paper we look at other spacecraft with well-documented outgassing records, and we review the formation of thin ice films. A mix of amorphous and crystalline ices is expected for Euclid. Their surface topography depends on the competing energetic needs of the substrate-water and the water-water interfaces, and is hard to predict with current theories. We illustrate that with scanning-tunnelling and atomic-force microscope images. Industrial tools exist to estimate contamination, and we must understand their uncertainties. We find considerable knowledge errors on the diffusion and sublimation coefficients, limiting the accuracy of these tools. We developed a water transport model to compute contamination rates in Euclid, and find general agreement with industry estimates. Tests of the Euclid flight hardware in space simulators did not pick up contamination signals; our in-flight calibrations observations will be much more sensitive. We must understand the link between the amount of ice on the optics and its effect on Euclid's data. Little research is available about this link, possibly because other spacecraft can decontaminate easily, quenching the need for a deeper understanding. In our second paper we quantify the various effects of iced optics on spectrophotometric data.

35 pages, 22 figures, A&A in press. Changes to previous version: language edits, added Z. Bolag as author in the arxiv PDF (was listed in the ASCII author list and in the journal PDF, but not in the arxiv PDF). This version is identical to the journal version

References in corpus (14)

• The Gaia mission
• Gaia Early Data Release 3: Photometric content and validation
• Advances in the experimental exploration of water's phase diagram
• The James Webb Space Telescope Mission: Optical Telescope Element Design, Development, and Performance
• Heavy ion irradiation of crystalline water ice
• Euclid preparation. XVIII. The NISP photometric system
• Experience with the Hubble Space Telescope: 20 years of an archetype
• The Swift-UVOT ultraviolet and visible grism calibration
• The Effective Surface Area of Amorphous Solid Water Measured by the Infrared Absorption of Carbon Monoxide
• Refractive index and extinction coefficient of vapor-deposited water ice in the UV-Vis range
• Testing the limits of the Maxwell distribution of velocities for atoms flying nearly parallel to the walls of a thin cell
• Thermal Desorption of H2O-Ice: From Nanoscale Films to the Bulk
• Energy transfer and restructuring in amorphous solid water upon consecutive irradiation
• The optical loss study of molecular layer for a cryogenic interferometric gravitational-wave detector

Cited by in corpus (4)

• Euclid. I. Overview of the Euclid mission
• Euclid. III. The NISP Instrument
• Euclid: Early Release Observations -- Programme overview and pipeline for compact- and diffuse-emission photometry
• Euclid: Early Release Observations -- Overview of the Perseus cluster and analysis of its luminosity and stellar mass functions