Santiago Rodriguez

OWLS: a ten-year history in optical wireless links for intra-satellite communications

The application of Optical Wireless Links to intra- Spacecraft communications (OWLS) is presented here. This work summarizes ten years of developments, ranging from basic optoelectronic parts and front-end electronics, to different inorbit demonstrations. Several wireless applications were carried out in representative environments at ground level, and on in-flight experiments. A completely wireless satellite will be launched at the beginning of 2010. The benefits of replacing standard data wires and connectors with wireless systems are: mass reduction, flexibility, and simplification of the Assembly, Integration and Tests phases (AIT). However, the Aerospace and Defense fields need high reliability solutions. The use of COTS (Commercial-Off-The- Shelf) parts in these fields require extensive analyses in order to attain full product assurance. The current commercial optical wireless technology needs a deep transformation in order to be fully applicable in the aforementioned fields. Finally, major breakthroughs for the implementation of optical wireless links in Space will not be possible until dedicated circuits such as mixed analog/digital ASICs are developed. Once these products become available, it will also be possible to extend optical wireless links to other applications, such as Unmanned Air and Underwater Vehicles (UAV and UUV). The steps taken by INTA to introduce Optical Wireless Links in the Space environment are presented in this paper.

Estimating error rates in processor-based architectures

This paper investigates a new technique to predict error rates in digital architectures based on microprocessors. Three studied cases are presented concerning three different processors. Two of them are included in the instruments of a satellite project. The actual space applications of these two instruments were implemented using the capabilities of a dedicated system. Results of the fault injection and radiation testing experiments and discussions about the potentialities of this technique are presented.

Radiation Hardening of FPGA-Based SoCs through Self-Reconfiguration and XTMR Techniques

SRAM-based FPGAs are increasingly being used in space applications. However, there are still many concerns about the reliability of these devices in high-radiation environments, particularly due to the possibility of single-event upsets (SEUs) in the configuration memory. This paper presents an architecture for implementing radiation-hardened SoCs based on FPGAs. Previous works used triple module redundancy (TMR) techniques together with scrubbing mechanisms based on partial reconfiguration. However, these solutions required external configuration controllers that increased the system complexity and deviated the design from the SoC principles. The proposed architecture uses novel self- reconfiguration techniques in order to eliminate the need for external components, so that a full radiation-hardened SoC can be implemented in a single FPGA. Since self- reconfiguration allows for on-board remote hardware updates, reliability is tackled at two key levels: Radiation- hardened operation and hardware upgradeability to solve design errors.

The effects of proton irradiation on coolrunner-II - CPID technology

Nowadays, Complex Programmable Devices are highly demanded in space missions. In this sense, CoolRunner-II devices are very attractive due to their low-power consumption. However, there is no report on proton sensitivity for this technology until date. In this work proton irradiation tests were performed on these devices in the energy range from 6 to 63 MeV in both static and dynamic modes. The results reported allow considering these devices suitable for space applications.

Sensitivity Evaluation Method for Aerospace Digital Systems With Collaborative Hardening

Complexity of current digital systems and circuits involves new challenges in the field of hardening and measuring circuits sensitivity under SEEs. In this work, a new solution for evaluating the SEU sensitivity of space systems based on using programmable logic devices is proposed. This solution is able to perform a deep analysis of fault effects in systems with hardware functionality distribution, taking into account the high complexity of the hardware nodes (complex programmable logic devices) and their collaborative hardening properties.

The September 2002 Antarctic vortex major warming as observed by visible spectroscopy and ozone soundings

The record of O3 total column and NO2 obtained by visible spectroscopy at Ushuaia (55° S), Marambio (64° S) and Belgrano (78° S) and vertical ozone profiles from the latter station provide insight into the unprecedented major warming observed above Antarctica in the last week of September 2002. From 18 September to 25 September the temperature increased 54°C at the isentropic level of 700 K. The temperature anomaly was observed down to the level of 300 K in which a well‐defined tropopause was established. From comparison of the ozone profiles before and during the event, it can be seen that a fast increase in O3 took place basically above 500 K, but the layer where the ozone hole occurs was barely affected. Low potential vorticity values above Belgrano occurred only at levels above 500 K, confirming that the vortex split was confined to heights above the layer of the Antarctic spring depletion. The signature of poleward‐transported air is clearly visible from the NO2 column departure from the envelope of the previous years in all three stations. NO2 columns larger than typical for ozone hole conditions by 400% were observed at Belgrano. Diurnal variations provide evidence of non‐denitrified extra‐vortex air.

Study on the effect of multiple errors in robust systems based on critical task distribution

Error correction techniques allow system recovery but usually do not remove completely latent faults. Although system continues working properly, some components can store faulty data. Authors analyze the effect of accumulated errors and possible solutions for systems thought for autonomous operation like aerospace on-board equipment.

Error rate estimation for a flight application using the CEU fault injection approach

This paper aims at validating the efficiency of a fault injection approach to predict error rate on applications devoted to operate in radiation environment. Soft error injection experiments and radiation ground testing were performed on software modules using a digital board built on a digital signal processor which is included in a satellite instrument. The analysis of experimental results put in evidence the potentialities offered by the used methodology to predict the error rate of complex applications.