XMM-NEWTON Thermal Design and In-orbit Performance

Stramaccioni, D.; Faust, Thomas; Hinger, J.

doi:10.4271/2000-01-2372

Cited by 1 publication

(1 citation statement)

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“…The inorbit commissioning of the OM showed a chromatic throughput loss of 16-56% compared to pre-launch expectations, with the largest losses occurring in the UV (Kirsch et al 2005;Schartel et al 2022). This contamination is attributed to non-volatile hydrocarbons, as the OM detector is kept at 300 K, and the entire optics at 290 K (Stramaccioni et al 2000); surface contamination by water does not persist in a vacuum at these temperatures (Sect. 4.3).…”

Section: Xmm-newton Optical Monitormentioning

confidence: 99%

Euclid preparation

Schirmer¹,

al.²

2023

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Material outgassing in a vacuum leads to molecular contamination, a well-known problem in spaceflight. Water is the most common contaminant in cryogenic spacecraft, altering numerous properties of optical systems. Too much ice means that Euclid’s calibration requirements cannot be met anymore. Euclid must then be thermally decontaminated, which is a month-long risky operation. We need to understand how ice affects our data to build adequate calibration and survey plans. 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. We then review the formation of thin ice films, and find that for Euclid a mix of amorphous and crystalline ices is expected. Their surface topography – and thus optical properties – depend on the competing energetic needs of the substrate-water and the water-water interfaces, and they are hard to predict with current theories. We illustrate that with scanning-tunnelling and atomic-force microscope images of thin ice films. Sophisticated tools exist to compute contamination rates, and we must understand their underlying physical principles and uncertainties. We find considerable knowledge errors on the diffusion and sublimation coefficients, limiting the accuracy of outgassing estimates. We developed a water transport model to compute contamination rates in Euclid, and find agreement with industry estimates within the uncertainties. Tests of the Euclid flight hardware in space simulators did not pick up significant contamination signals, but they were also not geared towards this purpose; our in-flight calibration observations will be much more sensitive. To derive a calibration and decontamination strategy, we need to understand the link between the amount of ice in the optics and its effect on the data. There is little research about this, possibly because other spacecraft can decontaminate more easily, quenching the need for a deeper understanding. In our second paper, we quantify the impact of iced optics on Euclid’s data.

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Section: Xmm-newton Optical Monitormentioning

confidence: 99%