In most engineering applications, physical measurements are relied upon to gauge the performance and state of health (SOH) of a system during operation, as well as to collect data. The level of detail for any measurement depends on how critical it is; it follows that determination of physical phenomena will only be as good as the quality of the measurements taken during the design, build, test and flight of space systems. Quality measurements providing insight into the SOH of the system, as well as phenomena occurring in the surrounding environment, can be used to identify performance issues should they arise. Sensors, instrumentation and test support equipment (ground based) are the tools used to validate system performance in a space-relevant environment prior to launch, as well as to perform measurements during actual space flight. This chapter provides an overview of the measurement technologies, guidelines and associated test hardware used in the test and operation of spaceflight systems.

Spacecraft, which we will also refer to as satellites in this text, comprise one or multiple instruments and subsystems that enable measurements and/or observations, platform orientation, health monitoring and uplink/downlink communications. Generally, instruments are comprised of subsystems and subsystems are comprised of components. Thermal control system (TCS) design considerations are applied to all items onboard a spacecraft, and the most stringent requirements typically apply to items associated with instruments. This is because instruments typically carry specially designed hardware built to perform a specific type of measurement (or observation) in space. Adherence of spaceflight system operations to properly defined thermal parameters (i.e., requirements) enables the success of the thermal control system applied.

Cryogenics is an expansive technical topic that can easily fill a standalone text under the same title. This chapter is not intended to replace the extensive technical content that may be found in contemporary cryogenics engineering texts [1‒6]. Its goal is, rather, to provide the reader with some technical insights into basic cryothermal topics that arise in the design of cryogenic systems for space applications.

Over the course of the past several years, I have had the opportunity to teach spacecraft thermal design to both undergraduate and graduate students. In researching texts for my first year of teaching the subject, I quickly found that there was no textbook available that methodically walked the student through the process of thermal design and analysis of space-based systems. Standard heat transfer texts simply did not provide detailed content addressing thermal design considerations and constructs for analysis of space-based systems: contemporary engineering texts only provided a cursory overview of space-based conduction and radiation phenomena. Texts that explicitly addressed the topic of spacecraft thermal design did so in the context of an overall systems perspective, with thermal as one of several chapters dedicated to different subsystems. Other chapters covered topics such as mechanical, guidance navigation and control, electrical, etc. Last but not least there was a lack of detailed treatment of techniques and methodologies developed from fundamental heat transfer, thermodynamics and fluid dynamics principles. In creating the lecture content for my course, I found this limited the conveyance of important subject matter to students. Ultimately, the solution for providing course participants with a coherent stream of lecture content was to combine information in previously published texts on the subject with information I deemed important. Information was collected in written form as class notes and provided to students as the primary text for the course. Ironically, while it is some years since I became a lecturer in aerospace, the absence of a single introductory text for students on spacecraft thermal design persists. Arguably, this is a key void in the literature associated with space systems. This volume aims to fill that void with teaching materials covering the topic of spacecraft thermal design. I hope that the concepts and principles conveyed in this book will inspire early-career practitioners and students enrolled in space-based courses, and enable them to gain a fundamental understanding of the thermal environment in space, as well as the basic skills required to perform spacecraft thermal design and analysis.

At the end of Chapter 4 we had begun to perform temperature analysis of components internal to a SpaceCube in LEO. In the analysis procedure we determined that it would be necessary to implement a thermal coupling between the E-box and the radiator in order to remove heat from the E-box and reduce its operational temperature.

In Chapter 1 the Stefan‒Boltzmann Law (shown in equation 3.1) was presented as the relation used to determine the amount of radiative thermal energy emitted from a surface.

Thermal conduction is one of the two primary heat transfer mechanisms present on space-based platforms. The goal of this chapter is to establish proficiency in the design and interpretation of thermal conductance resistance networks. The geometries studied are assemblies and/or sub-assemblies with multiple components of variable shapes and sizes.

In the development of spaceflight hardware systems, items are designed to perform in various operational environments. When the environment for intended use is considered extreme, the hardware in question undergoes ruggedization during the design phase to insure proper functionality once it is placed in the operational environment. The success of the measures taken during the design phase to ruggedize a system is verified by a test regime imposed at various levels of assembly that expose the hardware to environmental extremes comparable to, and slightly in excess of, what is expected in the operational theater. This is known as design, development and environmental testing. This chapter examines the philosophy behind environmental test practices for spaceflight thermal systems and looks at practical considerations associated with design and ground testing.