The imaging spectroscopy is a very powerful tool for the Remote Sensing of the Solar Planets and, in particular, of the Earth. This technique permits to get not only the geometrical information but also the spectral information of the scenario under observation. The number of potential data-products obtainable in this way could be very high, useful and of benefit in several fields of Earth Observation. If these are the advantages on the other side the new dimension will increase the number of data by the number of spectral band, and for this it will increase the technical requirements, mainly, on the Instrument Optical Design, Focal Plane Array, Storage/Compressor Data Unit, Data Transmission etc. The instruments able to produce 3-dimensional data (cube image) are the imaging spectrometers, which depending on the way how the spectral contents is obtained, can be divided in two main categories:
•The Fourier Imaging spectrometers
•The Dispersing Imaging spectrometers
Each one of the above categories of spectrometers has advantages and disadvantages and a choice between the two types can be made only performing a trade-off with the mission requirements. The Italian Space Agency (ASI) from long time is promoting and funding, to industrial and scientific levels, several activities covering almost all the aspects related to the imaging spectroscopy: from the applications to the instruments, from the data compressors to future hyperspectral missions.
Purpose of this paper is to present the main results of the activities supported by ASI in this field with particular emphasis on the activities related to the studies and developments of new instruments.
ROSA (Radio Occultation Sounder of Atmosphere) is a space instrument which uses the Radio Occultation Technique
to provide highly accurate measurements of the atmospheric refractive indexes from which it is possible to derive,
atmospheric vertical profiles of temperature, pressure and humidity, as well as profiles of electron content in the
ionosphere. The measurements, generally, are made by using meteorological balloons, able to give a very detailed
atmospheric profiles but only on a local scale. From the space, ROSA, flying on a LEO orbit, is able to perform more
than 500 atmospheric profiles per day on a global scale,
The ROSA instrument is the core of a scientific program, of the same name, promoted by the Italian Space Agency
(ASI) to contribute to a better understanding of Climate Change. This program foresees the installation of the
ROSA instruments on several space missions and the developments of an ad hoc Ground Segment for the acquisition
and processing of the data.
The ISRO (Indian Space Research Organization) mission OCEANSAT-2 will be the first mission that will embark
ROSA. OCEANSAT-2 is an operative mission for the study of the Ocean that will be launched next July 2007.
ALISEO (Aerospace Leap-frog Imaging Static Interferometer for Earth Observation) is a prototype of a new imaging interferometer for Earth Observation from the Space. This instrument has been derived from the so called "static interferometers", which do not employ any moving part to optically scan the instrument field-of-view. The device acquires the image of an object with superimposed a pattern of autocorrelation functions of the electromagnetic field coming from each pixel. The complete interferogram, constituted by a system of vertical fringes, is retrieved by moving the observed target with respect to the imaging device. The dependence of the OPD on the radiation-source spectral content, has been addressed performing a set of measurements by spectrally pre-filtering a 600W halogen lamp by means of interference filters with bandwidth of 10nm. We also describe the procedure of pre-elaboration of the acquired data to retrieve the spectrum of at-sensor radiance (dark signal subtraction, spectral instrument response compensation, effects of vignetting and Fourier transform algorithm). Laboratory measurements obtained by ALISEO are presented and discussed. This instrument was partially developed under a contract of Agenzia Spaziale Italiana (ASI).
We present INCA, a prototype of a light and versatile camera covering the 1-5 microns wavelength range designed for ground based and space application. INCA has innovative optical solution such as aspherical mirrors obtained via ion-beam ablation, a new light cryogenic concept and a new philosophy of chip controller. Co-financed at the bread board level by the Italian Space Agency (ASI) INCA has been recently characterized and is now ready for a phase 2 development.