Space travel is hugely complex, and it takes brilliant minds to build a satellite platform that can accurately make long journeys to Earth’s orbit and beyond. However, obstacles abound in every step since it is a complex system consisting of numerous processes simultaneously to keep the satellite working. One such major problem is vibrations in the satellite platform, and even little vibrations can impair satellite functioning during pre-launch and powered flight.
These little vibrations do not just happen out of anywhere; they originate from various sources, preventing the device from attaining its total capacity. Along the same line, “microvibrations” is yet another thing space engineers worry about since they can happen from the satellite’s own moving components in orbit. In this article, we’ll cover how to detect microvibration, how they happen, and what can be done to control them.
Microvibrations in Satellite Platform
Before we jump onto everything else, let us understand what microvibrations are in the first place. Satellite microvibrations are small-amplitude mechanical vibrations that happen to owe to dynamic interactions. These microvibrations are typically within the range of micrograms to milligrams, usually occurring at frequencies from a couple of Hz up to a few hundred Hz.
Microvibrations have grown increasingly relevant in the past few years and are becoming a significant obstacle in the face of space exploration. There is increased demand for performance, which has further resulted in microvibrations.
There is now a trend by NASA and ESA to promote satellites with higher-performing instruments and payloads. However, this also demands a lot of pointing stability, instrument resolution, lower sensor operating temperatures, etc.
As mentioned, space agencies are becoming increasingly focused on building high-performance, lightweight satellites. But, this also means that instrument accommodation is now problematic. The lightweight structures result in more vibration and various higher microvibration frequency sources of disturbance. All this makes meeting these engineering requirements all the more difficult.
As a result, it’s not unexpected that the technical problems involved with understanding, monitoring, and reducing dynamic interactions, which generate microvibrations, are now growing in importance. This is now one of the most challenging and vitally significant issues for satellite systems engineering. Microvibrations have an impact on numerous satellites used for Earth observation and other space missions as well.
It is usual to experience satellite platform microvibration when the spacecraft is out there. However, too much of it can damage satellite platforms and sensors, and it is a typical challenge in remote sensing sectors and data processing.
High-frequency microvibrations affect image quality, whereas low-frequency microvibrations affect geometric positioning accuracy. Microvibrations of different frequencies harm remote sensing satellite data applications. Experts and researchers have conducted an extensive study on microvibration detection technologies recently.
Many earth observation satellites have even gone through these detection tests. There are two ways of satellite platform microvibration detection: 1) via direct detection (with the help of an attitude sensor) and 2) via indirect detection (with the help of a non-attitude sensor).
The former detects microvibrations based on the star tracker attitude and an angular velocity tracker. At the same time, the latter detection method uses satellite imagery, a star image, laser footprint coordination changes, and surveying products to identify microvibrations.
Sources of Microvibrations
Internal mechanisms produce these microvibrations that we discussed above. The mechanical devices placed onboard the satellite have internally rotating machineries like a Momentum Wheel (MW) and a Reaction Wheel (RW). These devices are mostly always placed on satellite buses.
Besides these two devices, cryopumps and cryocoolers can also produce disturbances due to the payload-generated vibration modes. Furthermore, instrument-internal mechanics like steering mirrors, filter wheel mechanisms, and scanning mirrors are also sources of microvibrations.
How to Control Microvibrations
Microvibrations from onboard satellite disturbances can substantially damage high-precision space optical instruments (HPSOIs) operating conditions in orbit. Some critical micro-vibration reduction technologies have been created in the last few years. Satellite micro-vibration reduction is primarily accomplished in three ways: payload isolation, disturbance source suppression, and transfer path suppression.
The first two ways primarily emphasize isolation and are the most practical methods for suppression. On the other hand, the third method is a unique suppression method designed for the integrated optical satellite (IOS). Using these three suppression methods, the structural performance of the satellites can be changed to manage fluctuations in the space environment.
The problem of satellite microvibration detection and reduction is becoming organizationally challenging because this problem is an observatory-level issue that involves several engineering disciplines such as Structures, Guidance, Navigation and Control, Loads and Dynamics, and so on.
The detection and reduction of microvibrations thus need observatory-level management, the communication of cross-disciplines, and just overall coordination for the success of the mission. Although several disciplines are involved in the process, the micro-vibration problems are usually led and solved by Guidance, Navigation and Control, Systems Engineering, and the Mechanical Systems team.
It is imperative to focus on and make vital architectural decisions early on. These will have long-term mission ramifications and consequences. More often than not, the success of a mission depends on the architectural decisions taken at the observatory level in the early phases. To make good decisions, a comprehensive process, along with a multi-disciplinary team who will detect these jitters at a satellite station, is essential.
Microvibrations are increasingly becoming a significant problem in satellite platform construction. However, reduction technologies and methods for detecting microvibration are being introduced to deal with the problem.
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