AstroSat-SkyWave 

The AstroSat- SkyWave intended to be  the first italian satellite system jointly  defined by a team endorsing the interests of  amateur-astronomers and radio-amateurs. The project had a high  scientific content too, due to the contiguity of interests and competences between the amateurs communities and the professional Researchers.  The educational value of the project is also outstanding because each spacecraft has enough room to accommodate additional small experiments of scientific or technological nature provided by third parties.

 The system consisted of two microsatellites,  around 50 to 60 kg each,  launched in a nominal polar orbit at 800 km altitude. One satellite will carry a 250 mm diameter fast telescope for three missions: the discovery of planets outside the Solar  system, observing variable stars, and imaging portions of the sky selectable on command.

The figures below show the optical satellite during the in-orbit deployment of the four solar panels, arranged in a petal-like congiguration. The upper part of the telescope is being presently shortened by lowering inside the spacecraft the focal plane array section. The right-hand picture , which is a 3D cut  of the telescope, shows the primary reflector, the two correcting lenses put at the entrance of  the telescope, the secondary reflector, and the opening through which the light passes to be focused on the FPA.  

The  second satellite, that could  be launched at a later date,  is planned to carry two payloads.

- a first payload will be a topside sounder, operating in the 0.3 to 10 MHz,  for routinely collecting information about the time-space variability of the ionosphere. The Mission aims at improving  the near-medium term predictions of the propagation in the HF bands.

- a  second payload, still under a feasibility evaluation, would be a multiband receiver operating in selected frequency slots from 1.4 to 24 GHz  connected to a 3 m diameter meshed parabolic antenna in-orbit deployed. This payload will serve to perform radiometric measurements of the radiofrequency emissions by radiostars or other celestial bodies.  The 3 m diameter meshed, foldable, antenna is the most critical item of the project. which is based on eight shaped ribs that support a flexible metallic mesh.  After the in-orbit deployment, the mesh is stretched between adjacent ribs to form a piecewise approximation of a paraboloid.  A RF transparent, hollow, dielectric  column hosts the multiband feed and supports the Cassegrain subreflector. 

Both satellites will carry a VHF/UHF transceiver for radio-amateur communications as well as a beacon for telemetry purposes. An S_band transmitter provided with repointable directive antenna, is also envisaged for downloading science data.

Models actually built .

We built a 1:1 SCALE mechanical and radiofrequency model of the Optical satellite. This has a dual purpose:

- performing RF tests ( patterns, matching) on the several antennas that will be installed on its body

- familiarize with the spacecraft internal volume where we need to put the various equiments of the bus and payloads

Besides, and mainly for advertisement, we built scale 1:3 models of both the optical and the RF microsatellites. The latter with its 1 m antenna ( 3 m diameter on the full scale satellite) is quite impressive,