US technology start-up Rydberg Vacuum Sciences (RVS) continues to chart a forward trajectory as a “go-to” equipment provider in the emerging test-and-measurement ecosystem supporting the development and validation of small-satellite space missions – broadly instruments with a mass ranging from 1 to 500 kg. More precisely, RVS is carving out a specialist niche in the provision of affordable, off-the-shelf thermal vacuum bake-out and thermal vacuum cycling products – core enabling technologies in the preflight qualification workflow for small satellites and their constituent components, subsystems and instrumentation.

The evolving market context here is instructive, one in which small-satellite developers are opening up commercial and scientific opportunities in applications as diverse as astronomical observation, remote sensing, environmental protection and asset tracking and logistics. At the heart of it all, small-satellite innovation is proceeding at pace, with established and new-entrant manufacturers, as well as academic research groups, squeezing more and more functionality into ever-decreasing payloads while further lowering the barriers to entry to the space industry.

Testing for mission-readiness

All of this translates into relentless downward pressure on the capital and operational expenditure of satellite developers and their engineering teams – not least when it comes to the exacting test programmes needed to qualify satellite systems for launch and, ultimately, long-term operation in orbit. A case study in this regard is the Center for Astronomical Adaptive Optics (CAAO) at the Steward Observatory, the research arm of the department of astronomy at the University of Arizona (Tucson, AZ). The CAAO team is also the latest addition to the growing network of RVS customers and, as such, has been putting the vendor’s thermal vacuum (TVAC) test chamber through commissioning and acceptance over the past couple of months.

“We’re building prototype research instruments – including adaptive optics systems, advanced IR and UV detectors, and high-performance cryostats – that will be incorporated into future space-based small-satellite telescopes,” explains Ewan Douglas, assistant professor and assistant astronomer at the Steward Observatory. Douglas, for his part, heads up a broad-scope research effort spanning space instrumentation, wavefront sensing and control, and high-contrast imaging of extrasolar planets and debris disks. “The TVAC chamber’s testing capabilities will enable us to advance the technical- and mission-readiness of our scientific instruments and satellite payloads,” he adds. “In this way, we hope to make University of Arizona responses to NASA funding proposals that much more compelling.”

The operational detail

For any prelaunch test programme, instrumentation developers like Douglas and his CAAO colleagues will typically generate a model of the temperature extremes a small-satellite mission is likely to experience once in orbit. That’s followed by an exhaustive programme of laboratory-based thermal vacuum testing – essential for iteration and validation of the modelling and to ensure that any localized heating/cooling units are having the desired effect on front-line research instruments and their associated hardware.

In this scenario, the RVS TVAC chamber allows developers to evaluate technology performance along multiple coordinates. A thermal vacuum cycling test, for example, will see the craft’s hardware and instrumentation put through its paces and subjected to a “step-and-repeat” programme of extreme hot and cold temperatures in a high-vacuum environment, while a thermal balance test aims to demonstrate the effectiveness of the craft’s thermal control systems for maintaining the temperature of key systems within predefined limits. There’s also a vacuum bake-out requirement, in which the satellite hardware is heated to high temperature under high vacuum to quantify levels of material outgassing (the products of which can adversely affect the functioning of on-board imaging systems, thermal radiators, solar cells and the like).

Herein lies another opportunity. For even while the CAAO team is pushing the performance limits of its space-based instrumentation, a parallel commitment to cost-reduction remains very much part of the R&D mix – not least in the deployment of commercial off-the-shelf (COTS) hardware and software (rather than the development of bespoke technology solutions). “A key use-case for the TVAC chamber involves taking COTS products – say an optical detector or an onboard computer – and making sure that they still work in a space-like environment,” says Douglas. “Space-qualified COTS technologies are fundamental to driving down the overall cost of small-satellite astronomy missions.”

Delivering versus requirements

Equally important is the emphasis that RVS puts on its own off-the-shelf thermal vacuum systems. Put another way, that means thermal testing at a palatable price-point while also ensuring that ease-of-use is paramount. “In responding to our call for proposals, RVS was competitive on price and delivered versus desired functionality,” notes Manny Montoya, CAAO technical manager, who heads up a diverse team of engineers, technicians and machinists supporting the research of Douglas and other astronomers at Steward Observatory.

The functionality in question covers a general-purpose vacuum test chamber that any small-satellite mission on the Tucson campus can use to investigate the effects of temperature extremes in high vacuum. What’s more, the TVAC chamber also gives Steward Observatory astronomers the ability to access vacuum regimes as low as 10^-8 Torr – an essential requirement when qualifying high-end instrumentation destined for scientific missions like Aspera. This NASA project, led by Steward Observatory astronomer Carlos Vargas, is developing an extreme-UV astrophysics small satellite that will map the warm-hot-phase coronal gas around nearby galaxy halos (and, in turn, shed light on galaxy formation and evolution).

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Thermal vacuum test systems: gearing up for preflight qualification of small satellites

Another CAAO must-have is vibration isolation, so that Douglas and his team can evaluate precision adaptive optics systems inside the TVAC test chamber. In this respect, RVS proposed a novel solution comprising an optical table suspended by pneumatic legs outside the vacuum chamber – a configuration that isolates the optics under test by dampening any vibrations coming through the building floor (from passing road traffic, for example, or from doors opening and closing).

“In responding to the request for proposals,” concludes Montoya, “RVS did a great job of understanding CAAO’s technical requirements and adapting the TVAC system accordingly – testament to the company’s extensive technical domain knowledge on thermal vacuum testing for research and industry applications.”

• RVS will be exhibiting at the 36th Annual Small Satellite Conference at Utah State University (6–11 August 2022).