## 6 Conclusions  
In this paper, we performed environmental tests on the deployable reflector antenna, which is the core payload of the SAR satellite, in STM phase. The environmental tests of the deployable reflector antenna are divided into structural tests to simulate the launch environment and thermal tests to simulate the orbital environment. The structural tests of the STM phase are divided into sinusoidal vibration and acoustic load tests to verify the structural stability for the launch process at the qualification level. The thermal balance tests to verify the thermal stability under the cold/hot balance conditions and obtain the temperature data for the correlation of the thermal analysis model. During each test, visual inspection was performed to check for damage to the specimen before/after each test. A series of low-level sine sweep test and low-level acoustic random test were performed to calculate the frequency and amplitude shift of the fundamental modes in each direction, during each test. Using these environmental tests, the structural/thermal stability of the deployable reflector antenna could be verified with respect to the environment specification. The result of environmental tests conducted at STM Phase will be applied to the correlation of structural/thermal analysis models to design and manufacture the qualification models of the deployable reflector antennas.  
Figure 9: Result of the thermal balance test; (**a**) the test configuration of the thermal balance test; (**b**) thermal mathematical model (TMM) with three patch heaters; the time history of (**c**) vacuum pressure and (**d**) shroud temperature within the duration of test consisting of I. the evacuation and transient phase into the cold condition II. the cold balance condition; III. the break time without test and transient phase into the hot condition, IV. the hot balance condition and V. the transient phase into the ambient condition.  
**Author Contributions:** Conceptualization, Y.Y.; methodology, D.-G.K.; software, H.-G.K. and D.-G.K.; validation, M.-J.K., H.-G.K., R.-H.D. and D.-G.K.; formal analysis, D.-G.K.; investigation, H.-G.K.; resources, R.-H.D. and Y.Y.; data curation, D.-G.K.; writing--original draft preparation, H.-G.K., R.-H.D. and D.-G.K.; writing--review and editing, M.-J.K. and K.-R.K.; visualization, H.-G.K.; supervision, K.-R.K.; project administration K.-R.K.; funding acquisition, K.-R.K. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This study was conducted with support from the Korea Research Institute for defense Technology planning and advancement and the Defense Acquisition Program Administration in 2021 (20-207-B00-011-001).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.  
**Conflicts of Interest:** Authors [PERSON], [PERSON], [PERSON], [PERSON], [PERSON] and [PERSON] were employed by the company Hanwha Systems. All authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.