###### Abstract  
A new method to design in-orbit synthetic aperture radar operational parameters has been implemented for the Korean Multi-purpose Satellite 6 mission. The implemented method optimizes the pulse repetition frequency when a satellite altitude changes from its nominal one, so it has the advantage that the synthetic aperture radar performances can satisfy the requirements for the in-orbit operation. Other commanding parameters have been designed to conduct trade-off between those parameters. This paper presents the new optimization method to maintain the synthetic aperture radar performances even in the case of an altitude variation. Design methodologies to determine operational parameters, respectively, at nominal altitude and in orbit are presented. In addition, numerical simulation is presented to validate the proposed optimization and the design methodologies.  
range ambiguity improvement; azimuth ambiguity improvement; noise equivalent sigma nouqut improvement; PRF selection 2021 13234213  
day. The darker color between 509 and 522 km means that the satellite is located over that altitude range more frequently over 522 km. On the WGS84 ellipsoid, the whole variation in altitude is about 30 km for the orbit eccentricity of 0.002. For the in-orbit operation, the operational parameters are calculated at the ground segment using the nominal altitude. The calculated parameters are then used to operate SAR. When the satellite has an altitude different from the nominal one, the ground segment uses the tables on the nominal swath and macro-command parameter, which are stored in database, to recalculate the actual in-orbit parameters at a new altitude that is predicted by the ground segment [7]. The SAR operational parameters are optimized based on the predicted altitude at the ground segment. Thus, the SAR performance and image quality strongly depend on accuracy of the optimized SAR operational parameter. The SAR operational parameters are generated using a SAR design and analysis tool to meet the SAR performance requirement [6]. The generation process calculates radar instrument parameters like PRF, the echo window timing, receiver gain settings, the azimuth antenna steering sequence. Such generation process is repeated for each scene on the ground to be imaged. The SAR performance parameters are traded off for the number of iterations to meet the SAR requirement.  
In this paper, a novel calculation method for the in-orbit SAR operational parameters is proposed. As before, the operational parameters are calculated using the nominal satellite altitude at the ground segment and then constructed as a database format. This paper proposes a new formula using PRF to calculate the actual parameter for the predicted altitude. Simulation results show that the proposed method improves the SAR performance even for altitude variation. This paper also investigates a reference angle. Numerical simulation for the swath design and the parameter optimization validates the effectiveness of the proposed method. This paper is organized as follows. Section 2 proposes design methodology to obtain the SAR operational parameter at the nominal satellite altitude. Section 3 proposes an optimization method to improve the SAR operational parameters on the condition of the altitude variation and performance measures that are expected from the previous heritage. Finally, Section 4 concludes this paper.