Héctor Guerrero

COTS-Based Wireless Magnetic Sensor for Small Satellites

We report on the utilization of a commercial off-the-shelf (COTS) magnetic sensor for the mission NANOSAT-01 and the set of tests that have been developed to up-screen it. The magnetic sensor head is a Wheatstone bridge formed by four anisotropic magnetoresistances (AMR). AMR sensors are an adequate choice for medium- to high-sensitivity (~3 mV/V/G) and resolution (~ 3 ¿G) requirements, mostly due to their low weight and volume that are so interesting for the aerospace industry. The whole system installed in NANOSAT-01 is formed by two biaxial sensors with two redundant PCBs (printed circuit boards) of RAD-HARD proximity electronics, which conditions the AMR output signal, measure the temperature, and resets the AMR. This magnetic sensor belongs to the attitude control system (ACS) of the satellite.

Proton radiation effects in high power LEDs and IREDs for Optical Wireless Links for intra-Satellite communications (OWLS)

This paper presents data on proton displacement damage on light-emitting diodes (LEDs) and infrared emitting diodes (IREDs) of different technologies between 650 and 950 nm. 160 devices of a variety of 28 different COTS emitters were irradiated. Most irradiations were carried out with 52 MeV protons. Two components were also studied with 30 and 60 MeV protons. Light output and I-V characteristic curves were measured for emitters during the test. Injection enhanced annealing is also reported. As a result of this screening, 8 types of emitters have been identified as being tolerant to proton irradiation up to fluences of 2-1012 p/cm2. These issues are presented from the perspective of the work currently ongoing in the OWLS activities performed at INTA (Institute Nacional de Tecnica Aeroespacial of Spain). In this context, data about the first worldwide OWLS in-flight experience in the Spanish NANOSAT 01 are presented

Surface effects in magnetic nanoparticles measured by means of a magneto-optical method

Faraday rotation measurements have been made in samples composed of γ-Fe2O3 nanoparticles dispersed in a SiO2 matrix. All the samples show the same Fe∕Si molar ratio but different diameters of the magnetic nanoparticles. A magneto-optical method to measure the particle size using the Faraday effect is presented. The increase of Faraday rotation with the mean diameter of the γ-Fe2O3 particles can be associated with surface effects. The thickness value of their external layer with disordered spins has been obtained using a simple model and its high value suggests the large influence of the matrix on the magnetic properties of the composite.

Proton radiation effects on medium/large area Si PIN photodiodes for Optical Wireless Links for Intra-Satellite Communications (OWLS)

Components off the shelf (cots) photodiodes suitable for OWLS were irradiated with ~10 to ~60 MeV protons and up to fluences of ~2.5-1012 p/cm2. Electrical and optoelectronic parameters were measured during the test (I-V curves, dark current, responsivity and ideal diode factor). Results on degradation and post-annealing are reported. Preliminary results on the lattice effects are also pointed.

A study of the optical properties of photopolymer Fabry-Perot microcavities by a dual-wavelength fibre optic architecture

We present a novel method to study the behaviour of the optical properties of photopolymer materials with temperature. The photopolymer is deposited on the tip of optical fibres by dip coating to fabricate low-finesse Fabry-Perot microcavities. The signal processing technique utilized to interrogate the cavity is based on the generation of two quadrature phase-shifted interferometric signals using two Bragg fibre gratings. This technique enables the determination of the values of the thermo-optical coefficient and the linear coefficient of thermal expansion of the photopolymer. The effectiveness of the processing technique is also exploited in the study of the dependence of the temperature sensitivity on the cavity thickness.

Magnetic field biasing in Faraday effect sensors

A method for improving the performances of Faraday effect sensors, which is based in the passive magnetic field biasing of a Faraday rotator, is described. It allows obtaining reflective optical fiber sensor architectures, based on a single polarizer and a mirror-coated Faraday rotator, which exhibit linear response and maximum sensitivity. It can be achieved by means of a permanent magnet providing a 45° rotation of the polarization of the optical beam propagating through a Faraday rotator. Operation of this method in both a point magnetic field sensor and a current sensor, with a ferromagnetic ring as concentrator, has been demonstrated.

In-Orbit Measurement of SET and DD Effects on Optical Wireless Links for Intra-Satellite Data Transmission

In-orbit measurements of two experimental optical-wireless data links on board a polar LEO (Low Earth Orbit) spacecraft are presented. The effects of single event transients on the bit error rate, as well as those of displacement damage on the optoelectronic components being used, were measured. The results are consistent with those obtained from proton irradiations carried out in ground facilities.

OpticalWireless Links for Intra-Satellite Communications: Reflection Models and Hardware Optimization

The present work is a study on the propagation channel (physical layer) for wireless infrared communications in intra-satellite environments. Substituting cables and connectors with optical links inside a spaceborn platform offers many advantages and represents some technical challenges. We show analytical calculations, simulations, and experimental results for reflection models for aerospace materials, as well as wavelength division multiple access techniques for channel multiplexing. Improvements in the selection and optimization of emitter‐detector pairs are also presented.

Total Ionizing Dose Radiation Test on the Temperature Sensor TMP36 from Analog Devices

TMP36 temperature sensors were irradiated with Co-60 gamma rays up to 35 krad(Si). This temperature sensor will be used as a total ionizing dose sensor in a radiation monitor that will be on board the Spanish Earth observation satellite SEOSAT/INGENIO. Several samples were irradiated at different dose rates while their response was continuously measured. The sensitivity of the TMP36 to the total ionizing dose has been assessed by studying the evolution of the next three metrics: the output voltage, its temperature dependence and the power consumption. It has been observed that the degradation of these parameters increase significantly at doses higher than about 7 krad(Si), independently of the dose rate.

Magnetostriction measuring device based on an optical fiber sensor with an annular photodiode

A new simple and sensitive dilatometer to measure magnetostriction of ribbons has been developed, based on an optical fiber sensor using an annular photodiode. The optical fiber is used bidirectionally, both for emission and detection of light, simplifying the access to the ribbon under test. The working principle is based on the measurement by reflection of the longitudinal displacement of the ribbon end. For a Vitroperm amorphous ribbon of 100 mm length, 21 microm thickness, and 8.3 mm width, a displacement of 2.571 microm with a maximum uncertainty of 8 nm has been obtained.