The amount of space debris orbiting the earth is increasing. More than 700 000 objects with critical sizes of more than 1 cm have the potential to cause severe damage to space-based infrastructure. Improving the sensitivity of next generation space surveillance RADARs is necessary for the ability to detect space debris with sizes down to 1 cm. For a successful detection, a key parameter is the signal-to-noise ratio (SNR). Therefore the Fraunhofer Institute for High Frequency Physics and Radar Technique (FHR) analyses cryogenic cooled receivers for space surveillance RADAR systems. In addition to electrical frequency, the requirements of a mechanical design for a large cryo-cooled phased array receiver is challenging. In previous papers, an interim stage 7-element cryogenic receiver with cold antennas was mentioned as well as first studies of a scalable RF unit cell. The present paper shows the prototype and first results of a 37 – element phased array receiver, based on simulations. The design of a cryogenic phased array requires thermal and mechanical simulations in consideration with the modular design concept including the scalable unit cell. Referring to the German Space Surveillance Tracking RADAR (GESTRA) operating in L-band leads to the large receiver size due to the free-air wavelength of 23 cm. This paper presents our approach in the design of a 37 cryogenic phased array. It presents the simulation with focus on thermal transitions, heat loads and mechanical stress.

In the last 20 years, 2-stage cryocoolers have been found to provide an optimum solution for a wide range of applications like low temperature physics, superconducting cold electronics, cryopumping and superconducting magnets. For a proper design of helium cryostats with significant cold masses connected to the first and second stages of cryocoolers, it is important to have a load map (also called "working field") in order to estimate cool-down and warm-up time periods. Such load maps are either not presented in the open literature sources for "high" temperature ranges, or just given by manufacturing companies for general information but without any guarantee. In the present paper, the load map of a 2-stage Sumitomo 415DP cryocooler in the wide temperature range of 40-400 K is presented.

The amount of space debris orbiting the earth is increasing. More than 700 000 objects with critical sizes of more than 1 cm have the potential to cause severe damage to space-based infrastructure. As a consequence an improvement of the detection sensitivity of next generation phased array radar systems for space surveillance is of high importance. A key parameter for successful detection is the signal-to-noise ratio (SNR). The purpose of our study is to enhance the SNR of a radar system by cryogenic cooling of critical electronic devices of the receiver, contributing most to the system noise temperature. Cryo-cooling receiver systems and the underlying fundamental techniques are already known in Radio Astronomy. The Fraunhofer Institute for High Frequency Physics and Radar Techniques (FHR) has the goal to gain practical experience with low temperature techniques in order to find possibilities for implementing cryo-cooled electronics improving the SNR of phased array radar systems. Currently, the FHR team is in the early phase of adapting this technology to phased array radar systems. The final mechanical realization of a cryo-cooled antenna system for radar applications, including the corresponding electronics, will be an important contribution for future radar technologies