# A Double Vacuum Window Mechanism for Space-borne Applications

## TL;DR

This paper introduces a double vacuum window mechanism suitable for space applications, enabling a movable resealable window in series with a fixed one, demonstrated on a balloon-borne cosmic microwave background instrument.

## Contribution

It presents a novel vacuum window mechanism with a movable resealable window for space-borne instruments, demonstrated on a balloon payload.

## Key findings

- Successful operation with the EBEX balloon payload
- Enables optical access at atmospheric pressure while maintaining vacuum integrity
- Applicable to space-borne instruments requiring dual vacuum windows

## Abstract

We present a vacuum window mechanism that is useful for applications requiring two different vacuum windows in series, with one of them movable and resealable. Such applications include space borne instruments that can benefit from a thin vacuum window at low ambient pressures, but must also have an optically open aperture at atmospheric pressures. We describe the implementation and successful operation with the EBEX balloon-borne payload, a millimeter-wave instrument designed to measure the polarization of the cosmic microwave background radiation.