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ESA and NASA conducted a joint Galileo/GPS space receiver experiment on-board the International Space Station (ISS). The objectives (Enderle 2017) of the joint project were to demonstrate the robustness of a combined Galileo/GPS waveform uploaded to NASA hardware already operating in the challenging space environment - the SCaN (Space Communications and Navigation) software defined radio (SDR) testbed (FPGA) - on-board the ISS. These activities data included the analysis of the Galileo/GPS signal and on-board Position/Velocity/Time (PVT) performance, processing of the Galileo/GPS raw data (code- and carrier phase) for Precise Orbit Determination (POD), and validate the added value of a space-borne dual GNSS receiver compared to a single-system GNSS receiver operating under the same conditions. This paper will provide a general overview of the Galileo/GPS experiment – called GARISS - on-board the ISS, describe design, test and validation and also the operations of the experiment. Further, the various analysis conducted in the con is joint project and also the results obtained will be presented with a focus on the (Precise) Orbit Determination results.

The SCaN Testbed is an advanced integrated communications system and laboratory facility installed on the International Space Station (ISS) in 2012. The testbed incorporates a set of new generation of Software Defined Radio (SDR) technologies intended to allow researchers to develop, test, and demonstrate new communications, networking, and navigation capabilities in the actual environment of space. Qascom, in cooperation with ESA and NASA, is designing a Software Defined Radio GalileoGPS Receiver capable to provide accurate positioning and timing to be installed on the ISS SCaN Testbed. The GalileoGPS waveform will be operated in the JPL SDR that is constituted by several hardware components that can be used for experimentations in L-Band and S-Band. The JPL SDR includes an L-Band Dorne Margolin antenna mounted onto a choke ring. The antenna is connected to a radio front end capable to provide one bit samples for the three GNSS frequencies (L1, L2 and L5) at 38 MHz, exploiting the subharmonic sampling. The baseband processing is then performed by an ATMEL AT697 processor (100 MIPS) and two Virtex 2 FPGAs. The JPL SDR supports the STRS (Space Telecommunications Radio System) that provides common waveform software interfaces, methods of instantiation, operation, and testing among different compliant hardware and software products. The standard foresees the development of applications that are modular, portable, reconfigurable, and reusable. The developed waveform uses the STRS infrastructure-provided application program interfaces (APIs) and services to load, verify, execute, change parameters, terminate, or unload an application. The project is divided in three main phases. 1)Design and Development of the GalileoGPS waveform for the SCaN Testbed starting from Qascom existing GNSS SDR receiver. The baseline design is limited to the implementation of the single frequency Galileo and GPS L1E1 receiver even if as part of the activity it will be to assess the feasibility of a dual frequency implementation (L1E1+L5E5a) in the same SDR platform.2)Qualification and test the GalileoGPS waveform using ground systems available at the NASA Glenn Research Center. Experimenters can have access to two SCaN Testbed ground based systems for development and verification: the Experimenter Development System (EDS) that is intended to provide initial opportunity for software testing and basic functional validation and the Ground Integration Unit (GIU) that is a high fidelity version of the SCaN Testbed flight system and is therefore used for more controlled final development testing and verification testing.3)Perform in-orbit validation and experimentation: The experimentation phase will consists on the collection of raw measurements (pseudorange, Carrier phase, CN0) in space, assessment on the quality of the measurements and the receiver performances in terms of signal acquisition, tracking, etc. Finally computation of positioning in space (Position, Velocity and time) and assessment of its performance.(Complete abstract in attached document).

SAX is a satellite for X-Ray astronomy. It is a major element of the overall basic Science Program of the Italian Space Agency (ASI) and is being developed with the contribution of the Netherlands Agency for Aerospace Programs (NIVR). The scientific objectives of SAX are to carry out systematic and comprehensive observations of celestial X-Ray sources over the 0.1 - 300 KeV energy range with special emphasis on spectral and timing measurements. The satellite will also monitor the X-Ray sky to investigate long-term source variability and to permit localization and study of X-Ray transients. Alenia Spazio is developing the satellite that is intended for launch in the second half of 1995 in a low, near-equatorial Earth orbit. At system level a Structural Thermal Model (STM) has been conceived to verify the environmental requirements by validating the mechanical and thermal analytical models and qualifying satellite structure and thermal control. In particular, the following tests have been carried out in Alenia Spazio, CEA/CESTA and ESTEC facilities: Modal Survey, Centrifuge, Acoustic, Sinusoidal/Random Vibration and Thermal Balance. The paper, after a short introduction of the SAX satellite, summarizes the environmental qualification program performed on the SAX STM. It presents test objectives, methodologies and relevant test configurations. Peculiar aspects of the test campaign are highlighted. Problems encountered and solutions adopted in performing the tests are described as well. Furthermore, test results are presented and assessed.

SAX satellite verification is based on a protoflight approach, in which only one system model is realized at flight standard level, taking into account the utilization of hardware already qualified for other space programs and the necessity to respect the schedule constraints for a scientific objective. In any case, this approach was tailored with some deviations in order to reduce risks inherent in such a choice. The protoflight approach was also pursued at subsystem/unit level in particular for those subsystems and units considered critical from the schedule point of view. Payload Instruments followed the same approach but complete spare units were developed to reduce the risks associated with such an approach. A description of the model philosophy is provided and then, at satellite level, the testing approach and rationale for each model is presented. Finally, a brief description of each test will be given, highlighting objectives, methodologies, and test configurations. Moreover, for the major tests, problems encountered and solutions applied in establishing a correct approach are described.