Aalto-1 nanosatellite – technical description and mission objectives

摘要

This work presents the outline and so far completed design of the Aalto-1science mission. Aalto-1 is a multi-payload remote-sensingnanosatellite, built almost entirely by students. The satellite aims for a500–900 km sun-synchronous orbit and includes an accurate attitudedynamics and control unit, a UHF/VHF housekeeping and S-band data links,and a GPS unit for positioning (radio positioning and NORAD TLE's areplanned to be used as backup). It has three specific payloads: a spectralimager based on piezo-actuated Fabry–Perot interferometry, designedand built by The Technical Research Centre of Finland (VTT); a miniaturisedradiation monitor (RADMON) jointly designed and built by Universities ofHelsinki and Turku; and an electrostatic plasma brake designed and built bythe Finnish Meteorological Institute (FMI), derived from the concept of thee-sail, also originating from FMI. Two phases are important for thepayloads, the technology demonstration and the science phase. The emphasis isplaced on technological demonstration of the spectral imager and RADMON, andsuitable targets have already been chosen to be completed during that phase,while the plasma brake will start operation in the latter part of thescience phase. The technology demonstration will be over in a relatively shorttime, while the science phase is planned to last two years. The sciencephase is divided into two smaller phases: the science observations phase,during which only the spectral imager and RADMON will be operated for6–12 months and the plasma brake demonstration phase, which is dedicated tothe plasma brake experiment for at least a year. These smaller phases arenecessary due to the drastically different power, communication and attituderequirements of the payloads. The spectral imager will be by far the mostdemanding instrument on board, as it requires most of the downlinkbandwidth, has a high peak power and attitude performance. It will acquireimages in a series up to at least 20 spectral bands within the 500–900 nmspectral range, forming the desired spectral data cube product. Shortlybefore an image is acquired, the parallel visual spectrum camera will take abroader picture for comparison. Also stereoscopic imaging is planned. Theamount of data collected by the spectral imager is adjustable, and rangesanywhere from 10 to 500 MB. The RADMON will be on 80% of an orbitperiod on average and together with housekeeping data will gather around2 MB of data in 24 h. An operational limitation is formed due to theS-band downlink capability of 29–49 MB per 24 h for a 500 900 kmorbit altitude, as only one ground station is planned to be available for thesatellite. This will limit both type and quantity of spectral imager imagestaken during the science phase. The plasma brake will in turn be withinan angle of 20° over the poles for efficient use of the Earth'smagnetic field and ionosphere during its spin-up and operation.