within their allowable temperature range. All of the electronic instruments on board the spacecraft, such as cameras, data-collection devices, batteries, etc., have a fixed operating temperature range. Keeping these instruments in their optimal operational temperature range is crucial for every mission. Some examples of temperature ranges include Batteries, which have a very narrow operating range, typically between −5 and 20 °C. Propulsion components, which have a typical range of 5 to 40 °C for safety reasons, however, a wider range is acceptable. Cameras, which have a range of −30 to 40 °C. Solar arrays, which have a wide operating range of −150 to 100 °C. Infrared spectrometers, which have a range of −40 to 60 °C. Current technologies Coating Coatings are the simplest and least expensive of the TCS techniques. A coating may be paint or a more sophisticated chemical applied to the surfaces of the spacecraft to lower or increase heat transfer. The characteristics of the type of coating depends on their absorptivity, emissivity, transparency, and reflectivity. The main disadvantage of coating is that it degrades quickly due to the operating environment. Multilayer insulation (MLI) Multilayer insulation (MLI) is the most common passive thermal control element used on spacecraft. MLI prevents both heat losses to the environment and excessive heating from the environment. Spacecraft components such as propellant tanks, propellant lines, batteries, and solid rocket motors are also covered in MLI blankets to maintain ideal operating temperature. MLI consist of an outer cover layer, interior layer, and an inner cover layer. The outer cover layer needs to be opaque to sunlight, generate a low amount of particulate contaminates, and be able to survive in the environment and temperature to which the spacecraft will be exposed. Some common materials used for the outer layer are fiberglass woven cloth impregnated with PTFE Teflon, PVF reinforced with Nomex bonded with polyester adhesive, and FEP Teflon. The general requirement for the interior layer is that it needs to have a low emittance. The most commonly used material for this layer is Mylar aluminized on one or both sides. The interior layers are usually thin compared to the outer layer to save weight and are perforated to aid in venting trapped air during launch. The inner cover faces the spacecraft hardware and is used to protect the thin interior layers. Inner covers are often not aluminized in order to prevent electrical shorts. Some materials