Publication: Desarrollo de las dos torres: monitor de protones de base optoeléctrica para uso espacial. Primeros datos en órbita LEO a bordo del satélite Nanosat-1B
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2016-02-12
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Universidad Complutense de Madrid
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Abstract
En este trabajo de tesis doctoral se presentan el desarrollo, la calibración y los primeros resultados en vuelo, a bordo del satélite NANOSAT-1B, de las "Unidades optoeLectrónicAS para un DOSímeTrO y espectRómetRo ESpacial" (Las Dos Torres – LDT). LDT es un monitor de radiación de base optoelectrónica, sensible a los daños por desplazamiento (DD) que producen algunas partículas energéticas (como los protones), y sensible a los efectos transitorios que producen las radiaciones ionizantes (como rayos gamma, electrones o los propios protones). LDT utiliza dos dispositivos comerciales (COTS – Commercial Off-The-Shelf) optoelectrónicos, un LED y un fotodiodo, como elementos sensibles a la radiación. En concreto, LDT tien tres modos de trabajo, que coinciden con las tres medidas que realiza para caracterizar el entorno de radiación. Las tresmedidas que realiza son: (1) la degradación de la potencia óptica del LED que es proporcional a los DD inducidos por la radiación; (2) la señal de ionización directa que es proporcional al flujo de partículas ionizantes (como los p+); y (3) el aumento de la corriente de oscuridad que es también proporcional a los DD. Con este último modo de trabajo se ha conseguido resolver los problemas asociados al annealing. Resolver los problemas con el anneling ha permitido desarrollar un nuevo sensor de DD de reducida masa y consumo eléctrico, que es capaz de integrar todo el daño recibido incluso estando apagado, tomando ventaja además de su uso activo como monitor de flujo en tiempo real. NANOSAT-1B es un satélite desarrollado por el Instituto Nacional de Técnica Aeroespacial (INTA) que fue inyectado en una órbita baja (LEO – Low Earth Orbit) polar en julio de 2009. Combinando los tres modos de trabajo LDT puede medir de forma directa la dosis total de desplazamiento (TNID – Total Non-Ionising Dose) expresada como fluencia equivalente de protones, y el flujo equivalente de protones. Para verificar el correcto funcionamiento de los tres modos de medida, se han comparado los resultados entre ellos, se han comparado con los datos medidos por un dosímetro comercial tipo RadFET Resumen xx embarcado en el NANOSAT-1B, se han comparado también con datos procedentes de monitores de radiación de otros satélites y, finalmente, con simulaciones basadas en diferentes modelos teóricos del entorno de radiación de una órbita LEO. Usando las medidas de los flujos equivalentes de protones se ha mapeado la Anomalía del Atlántico Sur (AAS) a diferentes alturas. Con los datos de estos mapas se ha construido un modelo experimental de la radiación de la órbita LEO de NANOSAT-1B que se ha denominado MOLPN (Modelo Operativo Local de Protones atrapados de NANOSAT-1B). Se ha encontrado que el MOLPN proporciona valores muy similares al modelo llamado PSB97. Con ayuda del MOLPN se describirá un método de detección de fluctuaciones del entorno de radiación producidas por eventos o tormentas solares. Con todo este desarrollo se ha demostrado que el sensor basado en la corriente de oscuridad funciona correctamente, y es apto para medir los DD en órbita, tras aplicar ciertas correcciones basadas en su annealing que constituían un verdadero problema para la utilización de esta tecnología como sensor de radiación. Se ha conseguido elevar su madurez tecnología hasta el máximo nivel (TRL 9). Este nuevo sensor de DD ha sido ya incluido en diferentes misiones de exploración del planeta Marte, en dos instrumentos que el INTA ha desarrollado para las misiones MetNet Precursor y Exomars 2016 y se espera que en Mars 2020, y quizá en Exomars 2018
This work shows the development, calibration and first in-flight results on board of NANOSAT-1B SATELLITE of the space radiation monitor called “Las Dos Torres – LDT” (Unidades optoeLectrónicAS para un DOSímeTrO y espectRómetRo Espacial). LDT is a radiation monitor sensitive to the displacement damage (DD) produced by some energetic particles (like protons) in different optoelectronic detectors, as well as to non-cumulative effects produced by ionizing radiation (like gamma rays, electrons or protons). LDT uses two types of commercial optoelectronic devices (COTS - Commercial Off-The-Shelf), a Light-Emitting-Diode (LED) and a photodiode, as radiation-sensitive elements. Concretely, LDT allows the characterization of the radiation environment by measuring: (1) the degradation of the power emitted by the LED which is proportional to the DD induced by radiation; (2) the instantaneous ionization current generated in the photodiodes which is related to the flux of ionizing-particles (mainly protons for the NANOSAT orbit) crossing the detector at that moment; and (3) a measurement of the dark current of the photodiodes which is proportional to the DD induced by the radiation. The annealing effects affecting the last type of measurement have been compensated, so the device can measure the DD even when it is turned off. NANOSAT-1B is a satellite developed by the National Institute for Aerospace Technology (INTA), which was launched into a polar Low Earth Orbit (LEO) in July 2009. Combining its three working modes, LDT can directly measure the total displacement dose (TNID - Total Non-Ionising Dose) expressed as the equivalent fluence of protons, and the equivalent proton flux in real time. To verify the correct operation of the three measurement modes, we have compared the results obtained with each of other, and also with the data measured by a RadFET-type dosimeter that was also integrated in NANOSAT-1B. Finally, the results have also been compared with data from other radiation monitors, and with simulations based on different theoretical radiation models of the LEO orbit environment. Abstract xxii The South Atlantic Anomaly (SAA) has been mapped using the measurement of the equivalent proton flux at different heights. An experimental model describing the time and space dependence of the proton flux of the orbit of NANOSAT-1B, has been derived from all those measurements. It has been called MOLPN (Modelo Operativo Local de Protones atrapados de NANOSAT-1B – Local Operative Model for Trapped Protons of the orbit of NANOSAT-1B). It has been found that the MOLPN provides very similar values to the PSB97 model. A method for detecting radiation environment fluctuations caused by solar events using the MOLPN, has also been described. This development has finally shown that the annealing effects can be corrected and so the new sensor based on the measurement of the increment in the photodiodes dark current, is suitable for measuring the DD. With the described developments, the maximum Technology Readiness Level (TRL 9) has been reached. This DD sensor is going to be used within several instruments that INTA develops for different Mars exploration missions such as Mars MetNet Precursor, Exomars 2016, Mars 2020, and Exomars 2018.
This work shows the development, calibration and first in-flight results on board of NANOSAT-1B SATELLITE of the space radiation monitor called “Las Dos Torres – LDT” (Unidades optoeLectrónicAS para un DOSímeTrO y espectRómetRo Espacial). LDT is a radiation monitor sensitive to the displacement damage (DD) produced by some energetic particles (like protons) in different optoelectronic detectors, as well as to non-cumulative effects produced by ionizing radiation (like gamma rays, electrons or protons). LDT uses two types of commercial optoelectronic devices (COTS - Commercial Off-The-Shelf), a Light-Emitting-Diode (LED) and a photodiode, as radiation-sensitive elements. Concretely, LDT allows the characterization of the radiation environment by measuring: (1) the degradation of the power emitted by the LED which is proportional to the DD induced by radiation; (2) the instantaneous ionization current generated in the photodiodes which is related to the flux of ionizing-particles (mainly protons for the NANOSAT orbit) crossing the detector at that moment; and (3) a measurement of the dark current of the photodiodes which is proportional to the DD induced by the radiation. The annealing effects affecting the last type of measurement have been compensated, so the device can measure the DD even when it is turned off. NANOSAT-1B is a satellite developed by the National Institute for Aerospace Technology (INTA), which was launched into a polar Low Earth Orbit (LEO) in July 2009. Combining its three working modes, LDT can directly measure the total displacement dose (TNID - Total Non-Ionising Dose) expressed as the equivalent fluence of protons, and the equivalent proton flux in real time. To verify the correct operation of the three measurement modes, we have compared the results obtained with each of other, and also with the data measured by a RadFET-type dosimeter that was also integrated in NANOSAT-1B. Finally, the results have also been compared with data from other radiation monitors, and with simulations based on different theoretical radiation models of the LEO orbit environment. Abstract xxii The South Atlantic Anomaly (SAA) has been mapped using the measurement of the equivalent proton flux at different heights. An experimental model describing the time and space dependence of the proton flux of the orbit of NANOSAT-1B, has been derived from all those measurements. It has been called MOLPN (Modelo Operativo Local de Protones atrapados de NANOSAT-1B – Local Operative Model for Trapped Protons of the orbit of NANOSAT-1B). It has been found that the MOLPN provides very similar values to the PSB97 model. A method for detecting radiation environment fluctuations caused by solar events using the MOLPN, has also been described. This development has finally shown that the annealing effects can be corrected and so the new sensor based on the measurement of the increment in the photodiodes dark current, is suitable for measuring the DD. With the described developments, the maximum Technology Readiness Level (TRL 9) has been reached. This DD sensor is going to be used within several instruments that INTA develops for different Mars exploration missions such as Mars MetNet Precursor, Exomars 2016, Mars 2020, and Exomars 2018.
Description
Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Departamento de Óptica, leída el 18-12-2015