End to end simulators


End to end simulators include
SAR simulator and GNSS-R simulator
with a focus on ocean monitoring
with the possibility to set-up different
scenarios thanks to their modular configuration.

End to end simulators

Starlab specialises in the development of tailor-made simulators for a variety of Earth Observation technologies, either airborne or spaceborne. In this line, along its over 10 years of R&D activities, Starlab has developed a collection of detailed simulation tools, generally in support of European Space Agency (ESA) projects. These tools can be used to provide our customers with invaluable sets of fully-parametrisable synthetic data, or as the foundations for customised simulation software.

SAR simulator

Starlab developed its SAR simulator, on the basis of an activity requested by the European Space Agency. It is an End-to-End Simulator capable of representing a complete spaceborne and airborne interferometric SAR system: from the signal generation up to the final output product.

The simulator is built up by 8 building-block modules, each one responsible of a different part of the whole process:

1. Geometry Module: responsible for the computation of the position and velocity of the interferometric baseline and the geometric parameters defining the scene and the antenna configurations.
2. Sea Module: responsible for the computation of the parameters and variables related to the sea state.
3. Electromagnetic Scattering Module: responsible for the computation of the complex scattering coefficients of the sea surface.
4. Propagation and Atmospheric Module: responsible for the computation of the attenuation due to the atmospheric and free space propagation.
5. Instrument Module: responsible for the simulation of the transmission/reception chains and raw data simulation.
6. Synthetic Aperture Radar Processing Module: responsible for the SAR processing and the generation of the single look complex images.
7. Interferometric Processing Module: responsible for the interferometric processing simulation and phase multi-look.
8. Retrieval Module: responsible for the generation of the Level 2 data

The simulator underwent a thoroughly validation before it’s delivery to the European Space Agency and has already been used in various ESA projects, satisfying the requirements of the Client and of users communities.

Some of the key features of the simulator are:

Simulation of a geometry involving an ellipsoidal Earth surface (WGS84).
Generation of a sea surface with user input definitions, such as wind velocity, direction and fetch.
Inclusion of a complete scattering model based on the sea state.
A model to include the atmospheric and propagation attenuations.
Generation of various antenna patterns.
Generation of raw data for monostatic and bistatic channels.
A complete module of SAR processing allowing also for high-squinted observations.
A complete module of interferometric processing.
A sea-surface motion retrieval module.
Flexible customisation of the simulator at all levels. (orbit, signal, number of antennas, …).
Simulation of errors in position and baseline (interferometric case)
Simulation of scalloping effects and phase unbalances between channels (interferometric case).

GNSS-R simulator

Starlab originally developed the StarGym GNSS-R simulator for the European Space Agency. It is capable of generating GNSS-R signals as they were collected from ground, airborne and space platform, under different conditions of reflecting surfaces, various receiver parameters, different constellations, signals and frequencies.

StarGym is capable of simulating the complete GNSS-R scenario: geometry, sea surface electromagnetic scattering, atmospheric propagation and delay, reception chain, waveform and Delay-Doppler Maps (DDM) generation and inversion.

StarGym simulator can operate in three different modes:

1. Waveform mode: the DDM and waveforms are obtained through the integration of the radar equation as described in [Zavorotny and Voronovich, 2000].
2. Bitstream mode: the actual electromagnetic fields (both direct and reflected from the Earth surface) are computed for each signal sample. The DDM and waveform is then obtained not using the radar equation as the waveform mode but from direct correlation of the direct and reflected signals.
3. Interferometric mode: Same than previous module with the difference that instead of correlating the direct and reflected signals with a clean replica (generated by the simulator), a direct correlation between the direct and reflected signals is doing instead, thus allowing to simulate the interpherometric mode proposed by [Martin-Neira et al., 2009] for the PARIS IOD.

Other key features of the simulator are:

Generation of multiple GNSS signals and codes (GP,  Galileo, Beidou, EGNOS). These signals can be used independently or combine multiple of them in order to generate a composite code.
Simulation of a geometry involving a non-spherical Earth surface (i.e. WGS84)
Inclusion of a complete scattering model based on the generation of a sea surface.
Inclusion of an atmospheric module with a complete computation of both the neutral atmospheric and ionospheric delays.
 Complete receiver chain simulation (antenna pattern, amplification and down-conversion stage, …), coherent and incoherent integration stage to generate DDMs and inversion stage to retrieve geophysical parameters.
Graphical User Interface with several output windows that display the most relevant parameters of the simulator (waveform, DDM, antenna pattern, sea surface, …)
Flexible customization of the simulator at all levels (receiver, orbit, sea surface, signal analyser, …)