The Venµs mission is primarily designed for providing measurements over land surfaces. The objective is to offer the scientific community the opportunity to develop the use of high spatial and temporal resolution data. The Venµs mission will be a test bench for a future operational spacecraft constellation.
The objectives of Venµs mission are:
- to investigate and demonstrate the benefit of high revisit, high resolution remotely sensed measurements acquired by a superspectral imaging radiometer;
- to develop algorithms to exploit time series of data, including geometric and radiometric corrections, and to retrieve surface biophysical parameters;
- to foster the capability of the scientific community to use such new datasets and to develop innovative methods and applications.
Venµs mission requirements have been defined to serve scientific studies over land and possibly over coastal and inland waters, with focus on local and regional scale issues. It is expected that Venµs data will be useful:
- to monitor and analyze surface functioning under the influence of environmental factors (climate, topography, soils, etc.) as well as human activities;
- to study processes and their interactions with natural and human factors;
- to develop and validate natural and cultivated ecosystem functioning models and to help the improvement and validation of global carbon cycle models;
- to develop remote sensing data assimilation techniques within vegetation and surface flux models;
- to define theoretical and practical methods for scale transfer, i.e. up and downscaling;
- to help interpret data collected by low spatial resolution sensors;
- to develop, validate and implement land surfaces integrated model platforms.
Potential of Venµs reflectance time series: interest of constant observation angles
This property of Venµs images is one key of the enhanced quality of Venµs time series. A short note aims at showing the great interest of constant observation angles for the quality of reflectance time series, thanks to a data-set acquired with Formosat-2 satellite.
To fulfil its scientific objectives, Venµs has to acquire frequent, high resolution, multi-spectral images of over 100 sites of interest all around the world. The satellite will fly in a near polar sun-synchronous orbit at 720 km height. The whole system can be tilted up to 30 degrees along and across track. This configuration will result in a 2-day revisit time, 27 km swath, a camera resolution of 5.3 m at nadir, and the capability to observe any site under a constant view angle. The system will cross the equator at around 10:30 AM.
|Possible coverage of Venµs Nadir in yellow,
Tilted viewing in grey,
no coverage in blue
|Closer view of possible coverage
The satellite will carry a super-spectral camera characterized by 12 narrow spectral bands ranging from 415 nm to 910 nm. The band setting was designed to characterize vegetation status, including through red-edge bands, and to estimate the aerosol optical depth and the water vapour content of the atmosphere for accurate atmospheric corrections. The spectral band setting could also prove useful for coastal areas and inland waters studies.
The data will be acquired over existing or planned experimental sites with size ranging from 27 x 27 km² kilometres to 27 x 54 km² or more. All data for a given site will be acquired with the same observation angle in order to minimize directional effects. The baseline product for these selected sites is time composite images of geometrically registered surface reflectances at 10 m resolution. Strong efforts are devoted to provide high quality data, both in terms of radiometry (e.g. SNR around 100), geometry (e.g. multitemporal registration better than 3 m), and atmospheric corrections.
The Venµs scientific mission is planned for at least two years and a half and will be followed by the technological mission for a duration of one year.