## 1 Introduction  
Satellite thermal control methods that are currently used by conventional space missions are well established and proven. The term \"NewSpace\" is being adopted by many agencies and industries in recent days. According to experts, NewSpace is an approach focused on lowering the barriers of entry into space, by providing cheaper access to space and by commercializing the space sectors [1]. This has also further increased the interests among many small satellite manufacturers, research organizations, universities, and start-ups to build complex missions at a lower cost using nanosatellites and CubeSat platforms, especially for technology demonstration, science, research, educational projects, and commercial applications [2]. These nanosatellites typically weigh 1 to 10 kg and follow CubeSat size standards where 1U is a 10 \(\times\) 10 \(\times\) 10 cm\({}^{3}\) cube. There are other challenges in the new era of space technologies but this article focuses only on thermal management challenges on small satellites. Due to miniaturized electronics, high power components, and payloads, the satellite becomes heavily packed within the smaller satellite volume, and this leadsto thermal problems as the available radiative surface area is reduced [3; 4]. There is a necessity to solve thermal challenges for high power, scientific, and cryogenic small satellite missions. Taking advantage of small satellites, earth exploration missions are now being carried out using nano/microsatellites and are expected to grow exponentially [5; 6; 7]. Earth observation (EO) refers to the use of remote sensing technologies to monitor land, marine and atmosphere. Most of the earth observations are done in the infrared region of the electromagnetic spectrum. Infrared detectors that are designed to operate in the wavelength ranging from 0.76 \(\upmu\)m to 103 \(\upmu\)m need to be cooled down for better performance. The relationship between infrared wavelength and temperature is defined by Wien's displacement law in Equation (1) as follows,  
\[\lambda T=b \tag{1}\]  
where, \(b\) is Wien's constant (2898 \(\upmu\)mK), \(\lambda\)--Detection wavelength, and \(T\)--Low temperature. From this relation, it is clear that the radiation wavelength shifts toward the shortwave direction as the temperature rises. In general, the longer the infrared wavelength is, the lower the operating temperature of the detector will be [8]. Infrared detectors operating at a non-zero temperature are subjected to dark current (DC) noise which is directly related to pixel area, detector material properties and detector temperature. DC noise is the dominant limitation in many detectors and a relationship to calculate the DC is given in Equation (2) [9]. \[I_{DC}=C\times T^{2}\times A_{d}\times e^{\frac{\Delta Q}{kT_{d}}} \tag{2}\]  
where, \(I_{DC}\)--Dark Current intensity (\(A\)); \(C\) = Constant (1.2 \(\times\) 10\({}^{6}\) A\(\cdot\)m\({}^{-2}\)\(\cdot\)K\({}^{-2}\)); \(T_{d}\)--Pixel Temperature (K); \(\Delta Q\)--Energy band gap (eV); \(A_{d}\)--Pixel area (m\({}^{2}\)); Q--Electron charge (\(-\)1.6022 \(\times\) 10\({}^{-19}\) J); \(k\)--Boltzmann constant (1.38064852 \(\times\) 10\({}^{-23}\) J/K); T--Detector temperature (K). Dark current is significantly reduced when operating at lower temperatures, and hence most of the infrared detectors are required to be cooled to lower temperatures for certain applications. The low temperature requirement becomes of utmost importance for the detectors operating at the cryogenic temperature regime [8]. This study considers a mid-wave infrared (MWIR) instrument whose detector is required to be maintained between 0 to \(-\)100 \({}^{\circ}\)C for a few specific mission operations. Traditional passive thermal control methods are studied both numerically and analytically to analyze the effectiveness of the overall thermal control system in maintaining the payloads and components at required temperature levels.