VENµS

The VENµS (Vegetation and Environment monitoring on a New Micro-Satellite) is a successful Israeli-French collaboration that has contributed to science, technology, and education.

Mission Objective

VENµS’ mission has dual main goals – scientific and technological. Firstly, providing high-temporal and high-resolution images of about 150 sites in a high spectral range, for monitoring vegetation, land use, and environmental changes. Secondly, to test an electric propulsion system for a precise orbital control system in comparison to a standard fuel propulsion system.

Mission Significance

VENµS’ Earth observation abilities contribute to the improvement of climate and ecosystem models. Also being the first Israeli satellite equipped with an electric engine system, marks a significant national and technological achievement.

Source: CNES

Engineering Challenges

To meet its ambitious and diverse goals, VENµS has to overcome several technical challenges, the main among them:

• Optical Precision – For exploring and monitoring vegetation data, the multispectral imager must detect short-time surface reflectance variations, even below 1%. It means that even small light scattering could change the streaming data. Therefore, absolute stray light suppression is needed to accomplish this demand.
• Thermal Stability – Since the satellite is designated to orbit around the sun-synchronous orbit, it is exposed to high differences in temperature cycle, from -100°C to 120°C. Those high swings might cause deformation or disrupt the alignment in the imaging system. An advanced thermal control design is needed to prevent that.
• Altitude Accuracy Maintenance – For covering 50 sites in two days and to revisit those sites over and over, the satellite must perform high pointing accuracy, which means high altitude and orbit stability.
• Environmental Challenge – The fabrication and coating of the components have to include outgassing-resistant, UV-degradation, and atomic oxygen erosion, in order to prevent molecular or dust contamination of the optical path.

Instrument’s Characteristics

The satellite’s technological uniqueness is manifested by being a single multipurpose sensor and having an electrical propulsion system:

• VSSC (Venus SuperSpectral Camera) – high resolution optical imager which operates across the VNIR spectral range, with a 28m swath width and 30° tilting ability. It was built and constructed by CNES; its highly stabilized detectors and thermal control ensure consistent radiometric performance. It’s athermal optical bench, high-stability detectors, and dedicated thermal control ensure consistent radiometric performance.
• IHET (Israeli Hall-Effect Thruster) – The first Israeli-developed electric engine propulsion system was built by the IAI in cooperation with RAFEL. The principle of the system is using Xenon gas ionization to produce thrust and, by that, maintain the satellite altitude and inclination.

Acktar’s Solution

Acktar’s coatings are applied to optical and structural components to mitigate stray light impact and or maintain thermal control. Moreover, those coatings, such as Velvet Black or Magic Black, have the ability to adhere, thermal durability in vacuum, and less than 1% reflectance, which is suitable for extreme space environments. Acting like a blackbody surface, they prevent ghost reflections due to stray light and stabilize emissivity. By applying Vacuum Black coating, Acktar contributed to improving accurate data transmission.

Source: ESA

The Impact

VENµS delivered high-frequency, multispectral imagery that was used worldwide for climate research, including crop management and deforestation studies. Its data had a significant scientific impact on global climate science decisions and implications.

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