So far, INVAP’s most demanding venture in radar technology is its participation in the electronics of Argentina’s space-based Synthetic Aperture Radars (SAR). These systems are under current development as a joint undertaking of INVAP and the National Commission for Space Activities (CONAE), the Argentine Radioastronomics Institute (IAR) and INVAP. They are designed to fit the future SAOCOM satellites.
This technology is considered strategic by all countries, and each member of the small group possessing it had to create its own SAR blueprint. A SAR is quite more complex than ordinary control radars. The antenna is fixed but emits a moving RF beam which illuminates its target in slanting angles, generating alternatively illuminated and dark areas.
The weak echoes of such emissions are detected and digitally transformed into images, which have more field depth than optical images. SARs can operate at night, traverse cloud or smoke cover and also deliberate camouflage. The beam may even penetrate the ground to some extent. |
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Artist’s view of the SAR-L from above, with the radiant elements depicted in red. High energy consumption allows for just 10 minutes of use in every given orbit. |
The SAOCOM SAR operates in the L band (23 cm wavelength) and its antenna has an area of 25 square meters. This combination limits the size of discernable objects to 10 meters, and is therefore of little military value. Instead, these wavelengths penetrate the terrain, detecting humidity, underground water tables, and even the aqueous contents of vegetation (which shorter bands cannot do), so an L band space radar is a good choice for a real-time environmental, agricultural and catastrophe management probe.
The radioelectric design of these antennae was done by IAR, and the construction and deployment is executed by CONAE.
To power such large antennae calls for a big surface of high efficiency and long-lasting photovoltaic cells, developed by CNEA, as well as a heavy energy storage battery bank.
In the shared responsibilities of the SAOCOM undertaking, INVAP’s task is twofold. On the one hand, we are developing the core-electronics of the SAR-L radar, pulse generation and the definition of high-speed operational modes. On the other hand, we are also constructing the satellite platform able to house large components in a relatively low-weight (under 2 ton) satellite.
To diminish weight but not size, SAOCOM will use extensively carbon-fibre reinforced plastic, combined with aluminium honeycomb. All in all, this one satellite-type has proven to be one of the biggest challenges ever to INVAP’s space engineering so far.
SYNTHETIC APERTURE RADARS IN SPACE 
