Future Telecom missions will encounter a severe radiation environment, including the heart of the Earth's trapped electron radiation belts and the Solar Particle Events (SPE).
Additionally, the micrometeoroid environment is also of concern for future Telecom missions. The desire for microelectronics that are miniaturised, low power, and high speed, drives technology designa that are increasingly sensitive to radiation effects.
Radiation effects that are important to consider for instrument and spacecraft design fall roughly into four categories:
- Degradation from total ionising dose (TID),
- Degradation from non-ionising energy loss (NIEL),
- Single event effects (SEEs), and
- Spacecraft charging/ discharging.
Each effect requires a different environment definition depending on the physics of the effect and the interaction model used to predict the rate of occurrence.
In the proposed experiment, TID, NIEL and SEE effects are studied by employing several technology experiments in conjunction with radiation monitoring instruments, selected to provide optimised coverage of the region of the radiation environment most important for the effects being studied.
The AEEF is developed in order to have negligible impact on the main Alphasat mission. Presently power consumption, mass, TM/TC requirements, and the architecture are critically studied to achieve this objective.
The AEEF has the capability of providing the Alphasat with real time radiation and a micrometeoroid environment. The AEEF will provide alarm functions to the spacecraft in the case of increased radiation levels, enabling the spacecraft to carry out mitigation techniques protecting sensitive elements.
The scientific data provided offers a better understanding of the spacecraft environment resulting in better models, consequently reducing required margins and costs. The accompanying radiation effects package flight-tests important EEE Component technologies of several types applicable to future Telecoms missions. The objectives include full validation of hardness assurance methods used in design, validation of new testing and analysis methods and demonstration of novel EEE Component technologies. Additionally the validity of ground based testing compared to in-flight results is studied.
The Alphasat Environment and Effects Facility (AEEF) is composed of a number of different elements measuring specific environments and effects together with dedicated hardware for data storage and interface to the spacecraft. The environments monitored include:
- High energy radiation (from the radiation belt, solar flares and cosmic rays),
- Low energy electrons, and
- Micrometeoroids and debris.
- Single event effects (e.g. single event upsets, single event transients),
- Total Ionising Dose (TID) degradation (specifically of interest in the electron rich Alphasat environment),
- Displacement Damage (DD) to optoelectronics and detectors, and radiation background in sensors.
- Incident electrons in the overall energy range ~50 keV - >10 MeV,
- Incident protons from ~4 MeV to >300 MeV,
- Incident heavy ions in the Linear Energy Transfer (LET) range 15-70 MeV/mg/cm2,
- Total ionising dose measurements utilising RadFETs with sensitivity of up to 85 mV/rad.
The project is currently in phase A to study the feasibility of implementation of the AEEF on the Alphasat. This activity will be concluded at the end of July 2006.
This activity was initiated at the end of January 2006. Currently the detailed requirements for the AEEF are being generated.