COTS MOS Dosimetry on the MeMOSat Board, Results After 2.5 Years in Orbit.

JOSÉ LIPOVETZKY, MACARENA RODRÍGUEZ CAÑETE, GABRIEL REDIN, ADRIÁN FAIGÓN, MARIANO GARCÍA INZA , SEBASTIÁN CARBONETTO, MARTÍN ECHARRI, FEDERICO GOLMAR, FERNANDO GOMEZ MARLASCA, MARIANO BARELLA, GABRIEL SANCA, PABLO LEVY

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Simposio; 11 IIAA Latina American Syposium on Small Sateeelites Advanced Technologies and Distributed Systems; 2017

We present the results after 2.5 years in or-bit of Total Ionizing Dose (TID) measurements doneusing Metal Oxide Semiconductor (MOS) dosime-ters on the MeMOSat board. The MeMosat boardwas launched on July 19th 2014 at the BugSat-1?Tita? microsatellite developed by Satellogic to stayat LEO. We used as dosimeters p-channel Commer-cial Off The Shelf (COTS) MOS transistors with gateoxides of 250 nm. Before launch, a subset of transis-tors with similar drain current to voltage (I-V)curves where selected from a group of 100 devices.The temperature dependence of the (I-V) curves wasstudied to find the minimum temperature coefficientbiasing point. Then, a calibration subgroup of sen-sors was irradiated using a 60 Co gamma source tostudy their response to TID, showing responsivitiesof ~75 mV/krad when the sensors are irradiatedwithout gate bias. Also, the post irradiation responseof the sensors was monitored, in order to include acorrection for low dose rate irradiations, yielding30 mV/krad. A biasing and reading circuit was devel-oped in order to allow the reading of up to 4 sensors.The threshold voltage was monitored during differ-ent periods of the mission. After 2.5 years in orbit,the threshold voltage of the sensor mounted on theMeMOSat Board had a V T shift of approximately 35mV corresponds to a dose of 1.2 krads.