SPACE SAR system with integrated photonic BEAMforming

Project Information

SPACEBEAM

Grant agreement ID: 870421

DOI

10.3030/870421

Project closed

EC signature date 12 November 2019

Start date 1 January 2020

End date 30 June 2023

Funded under

• INDUSTRIAL LEADERSHIP - Leadership in enabling and industrial technologies – Space

Total cost

€ 3 098 751,25

EU contribution

€ 3 003 751,25

Coordinated by

SCUOLA SUPERIORE DI STUDI UNIVERSITARI E DI PERFEZIONAMENTO S ANNA
Italy

Periodic Reporting for period 2 - SPACEBEAM (SPACE SAR system with integrated photonic BEAMforming)

Reporting period: 2021-07-01 to 2023-06-30

Summary of the context and overall objectives of the project

Synthetic Aperture Radar (SAR) is a remote sensing technology finding applications in a wide range of fields, especially related to Earth observation. It enables a fine imaging that is crucial in critical activities, like environmental monitoring for natural resource management or disasters prevention. In this picture, the Scan-on-Receive (SCORE) paradigm allows for enhanced imaging capabilities thanks to wide swath observations at finer azimuthal resolution achieved by beamforming of multiple simultaneous antenna beams.
SPACEBEAM aims at designing, realizing and testing an innovative SCORE SAR receiver that will enable the concept of multiple beam SCORE for improved resolution.
In order to comply with the requirements of future swarms and constellations of low-Earth orbit satellites and cubesats in terms of performance, size, weight, power consumption and cost, the envisioned receiver will be based on an optical beamforming network realized as a photonic integrated circuit (PIC). The PIC will implement a precise, continuous beamforming of wideband RF received signals from an array of 12 antenna elements into 3 beams. At the same time, the PIC will also realize a frequency-agnostic photonic down-conversion of signals in the range from 5 to 40 GHz, so that the output signals can be directly digitized.
These innovative features make the SPACEBEAM PIC a powerful device for future Earth observation applications.
The PIC will be implemented using two materials platforms, to achieve a compact “hybrid” chip-assembly including several active and passive functions (lasers, detectors, modulators, filters, switches, delays, phase shifters). The PIC will be controlled using a novel actuation technique based on low-power consuming piezo elements. In order to push forward the maturity of the SPACEBEAM technology, the project will also develop and test a Space-compliant package for the PIC. The packaged PIC will be included in a specifically designed Engineering Model of the multi-beam SCORE-SAR sensor, to properly test the performance of the entire system.
The photonics-based SCORE SAR system will therefore show more functionalities, better performance, and lower size, weight, and power consumption than the current systems.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

Implementation of the hybrid PICs and of the Functional Models:
Four hybrid PIC assemblies have been delivered (3 PZT-based and 1 heater-based) for implementing the Functional Model (FuMo), and 2 PZT-based assemblies for the Elegant Breadboard (EBB). Some significant challenges have been encountered while building such a densely integrated chips, and specific solutions have been developed to overcome them. Moreover, specific control electronics equipment has been developed for the FuMo’s.

Test of the FuMo’s:
To establish the end-to-end performance of the FuMo, several intermediate tests had to be undertaken, which revealed issues with the integrity of the PIC elements after multiple tests, their performance drifting with time, and the possibility to easily tune every single element in the assembly given the limited number of monitoring ports.
Despite these challenges, it was possible to demonstrate a PIC design which satisfied a number of initial project requirements: frequency of operation, sideband filtering, down-mixing. Moreover, it has been possible to test the beamforming capability of the SPACEBEAM architecture. The results show the first-ever demonstration of multi-beam optical beamforming using a Blass matrix, implemented within a hybrid PIC.

Design and implementation of the hermetic package for the EBB:
The initial packaging approach based on the gold box has been substituted by a chiplet approach, in order to reduce the complexity and the cost of the of package development.
The developed package has demonstrated a leakage as low as 5e 7 mbar·l/s.

Design of the EBB electronics for driving the packaged PIC:
The control electronics for the EBB has been designed. Due to delays, it has been not possible to really develop it. Anyway, the design has defined the components requested for its implementation, using both COTS components as well as their space-grade equivalent devices. The maximum total power consumption has been estimated, confirming the feasibility of the size, weight, and power consumption targets of the project.

Environmental tests:
One of the available FuMo’s has undergone a radiation test and a thermal vacuum cycling test according to ECSS standards. These tests have confirmed the absence of blocking issues with respect to environmental reliability.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

Main progress beyond the state of the art:
• The project has pushed the complexity of hybrid PICs to a new level, developing probably the largest and more complex integrated MWP device ever conceived: 5 PICs coupled together, 2 fiber arrays, 16 RF I/O ports, and hundreds of DC controls.
• During its activity, the SPACEBEAM project has developed one of the first ever hybrid lasers based on PZT-controlled SiN, which can provide fast tuning with no thermal effects (though this feature has not been exploited during the project).
• The SPACEBEAM project has reported the first demonstration of a multi-beam optical beamforming using a Blass matrix. This is a milestone for the exploitation of photonics in radar beamforming.
• As a direct consequence of the complexity and size of the developed hybrid PIC, the SPACEBEAM project has developed probably the largest hermetic package for a hybrid PIC so far, where the dimension of the package has been determined by the number of RF and DC I/O ports, and the related ceramic fan-out. The identified technical solution based on the chiplet approach has allowed limiting the size of the package, and can be taken as a significant example in next development of large-size hybrid PICs.
• The SPACEBEAM project has delivered the first environmental test of a PZT-controlled SiN PIC.
• In the specific application concerning the SPACEBEAM radar receiver, it has been demonstrated by estimation that the photonics-based solution has lower SWaP than the digital beamforming counterpart.

Socio-economic impact and wider societal implications:
• SCORE-SAR is an advanced Earth observation technique that still has no in-field implementation. The proven reduction of SWaP guaranteed by the SPACEBEAM approach will make such advanced observation mode available even for smaller SAR missions.
• The data on SWaP confirm that the SPACEBEAM approach allows the implementation of SCORE SAR in small, micro and nano satellites, which can form constellations and swarms.
• The implementation of the SPACEBEAM packaged PIC has used EU-only technologies.
• The following advancements on integrated microwave photonics technologies can be claimed:
- improved maturity of PZT technology, which is fundamental for controlling complex PIC systems
- advancement on hermetic packaging of large iMWP systems
- advancement on space compliance of iMWP systems
All these technical outcomes have the potential to be taken off by the European industry

Functional Model, including hybrid PIC and control electronics

Hermetic packaged PIC

Intermediate version with ceramic and fanout PCB