AstroSat-SkyWave is a joint satellite project by UAI (Unione Astrofili Italiani, Italian Astroamateur Union) and AMSAT-I (AMateur SATellite Italy). The Project represents a world "first" in that, though amateur satellites have been launched and operated by radioamateurs and astronomy missions have been realized, on a small scale, by University's students, a complex and highly performant multipurpose multisatellite system has not yet been conceived by joint amateur groups having adjacent and partly common interests. AstroSat-SkyWave consists of 2 nanosatellites, around 50 kg each, launched in a polar orbit at 800 km altitude. The first satellite will carry a primary optical payload and auxiliary payload as well. The second satellite will carry 2 primary payload: a multiband receiver to establish, in cooperation with ground radiotelescopes, a SB-VLBI (Space Based Very Long Baseline Interferometer) operating in the 1.4 to 24 GHz bands; and a "topside sounder", basically a pulsed radar operating in the 0.3 to 10 MHz, for probing the Earth's atmosphere to assess the HF propagation effects from its ion content. A distributed Ground Segment, to both receive and process data, will complement the System.
THE FIRST SATELLITE (see image) to be launched will carry a 250 mm diameter, f/3.6 telescope for three missions:
a) Photometry: the mission aims at the discovery of extrasolar planets, through the observation of the starlight intensity variations vs time. The target observation area extends through + or - 40 degrees with respect to the ecliptic plane.
b) Imaging: this mission provides a space access to amateurs for planning and taking images of the sky exploiting the absence of the atmosphere and the long observation times feasible with inertial pointed satellites.
c) Spectrometry: this mission aims at gathering spectral information about the light emission of preselected stars. The spectrometer will cover the VIS to NIR bands with a resolution around 5 micron.
The telescope will be equipped with a mobile support holding 2 CCDs of 2000 x 2000 pixels each and an hole for letting pass the collimated beam towards a spectrometer underneath the focal plane. A 2nd priority payload would consist of a receiver operating in the 10 to 40 MHz bands for listening to the solar and jovian radioemissions. Small "opportunity payloads" might be accomodated within the nanosatellite mass and DC power margins. Among these, a small communication transceiver for the radioamateur community.
THE SECOND SATELLITE (see image) will carry 2 primary payloads:
1 - One will be a RECEIVER operating in selected frequency slots from 1.4 to 24 GHz connected to a 3 m diameter parabolic antenna in-orbit deployable. This payload will operate in 2 modes:
a) in a stand-alone mode it will perform radiometric measurements of the emissions by radiostars, providing information about the average signal power and its spectral feature enabling to compute the star relative speed from Doppler-Fizeau data
b) in the interferometric mode the satellite receiver will operate in synchronism with one or more ground radiotelescopes all looking at the same radio star hence receiving the same signal. The very long interferometer baseline between satellite and the ground terminals, wich could go up to 9000 km, allows achieving very high spatial resolutions
2 - A 2nd payload will be a TOPSIDE SOUNDER, basically a pulsed radar operating in the 0.3 to 10 MHz band. The EM pulses, downward directed, will interact with the electrically charged atmospheric layers, which will reflect a fraction of the incident energy depending on the ion content. The echos received and processed, will give a real time picture of the spatial and temporals variations of the ionosphere which has a deep impact on the radiowaves propagation below 10 MHz. Besides directly contributing to better the forecast of the propagation conditions more conductive to satisfactory long range ionospheric communications, the experiment will provide an important contribution to the widespread research effort on the "space weather".
Other small payloads, such as transceivers for amateur communications od additionally technology or scientific experiments, could also be carried compatibly with the available spacecraft resouces.
THE GROUND SEGMENT (see image) - Besides the TT&C and the Master Control Station, duplicated for reliability and availability reasons, the ground segment will be conceived with the following features:
- the radioamateurs could receive and elaborate the satellite telemetry data, transmitted in the UHF amateur band;
- amateurs participating to the "space weather" groups, could receive and elaborate the data acquired by selected spaceborne instruments such as the topside sounder;
- radioastronomers equipped with terminals enabling the reception of the interferometric data transmitted, at S-band, by the 2nd satellite can either receive the S-band downlinked data or connect, via internet, to the primary data station for two-way exchange
- educational institutions can interactively access, via internet, a repository of information, data and programmes enabling students to implement guided paths toward the acquisition of certain skills.
WHO WILL BENEFIT - Besides the amateur and professional scientific communities, the Project will contribute significantly to the activities of both Academic Institutions and High Schools, by:
- establishing cooperation agreements with selected University's Departments: by assgning thesis, or cofunding doctoral candidates;
- accepting young graduates as part-time or full-time volunteers in Project working-groups;
- defining training programmes with Technical High Schools to involve students in data reception and processing
