Radiation management, avionics development, and integrated testing of a Class-D space-based asteroid X-ray spectrometer

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2016.Cataloged from PDF version of thesis.Includes bibliographical references (pages 161-165).The Regolith X-ray Imaging Spectrometer (REXIS) is a student designed and built payload instrument aboard NASA's OSIRIS-REx asteroid sample return mission. The interplanetary target for this mission is a primitive asteroid known as Bennu that is believed to be relatively unchanged since the formation of the Solar System over 4.5 billion years ago. The primary goal of REXIS is to provide data to determine the elemental abundance composition of Bennu's surface through the measurement of X-ray fluorescence from Bennu's regolith. Achieving this goal requires the REXIS instrument to have an avionics system designed to operate the x-ray detectors, perform some preliminary processing of the x-ray events detected, and transfer this information to the main spacecraft computer for transmission to Earth. REXIS avionics accomplish these tasks using a mixture of commercial and spaceflight-grade hardware, reconfigurable Xilinx and Actel FPGAs, and a softcore MicroBlaze processor. Although the REXIS instrument is classified as a high-risk Class-D project by NASA, it must safely interface (in the manner of "do no harm") with the low-risk Class-B OSIRIS-REx spacecraft. Furthermore, REXIS must operate in the interplanetary space radiation environment of the OSIRIS-REx mission. This thesis details the REXIS avionics system and its novel features for collecting scientific x- ray data, interfacing safely with the OSIRIS-REx main spacecraft in spite of differing Class B/D risk postures, and robust operation in the interplanetary space radiation environment. Emphasis is placed on how the REXIS avionics design and radiation hazard mitigation features were implemented with significant budget and time constraints.by Pronoy K. Biswas.S.M

Study of trends in cross-section values of primary reactions of most abundant isotope of elements with Z= 6 to 116 induced by 14 MeV neutrons using TALYS code and the EXFOR database

Study was carried out to understand the trends of variation of cross-section values of all possible primary reactions induced by 14 MeV neutrons incident on the most abundant isotope of elements from atomic number 6 to 116. The available nuclear reaction channels and cross-section values of all possible primary reactions were obtained using the theoretical values calculated using TALYS nuclear code version 1.96. The trends were explained on the basis of nuclear binding energy curve, the pairing effect and shell effect. Most of the trends show a regular variation except at some points, which give interesting information for the nucleus where trend is irregular. The variation of the available experimental cross-section values obtained from the EXFOR database, if any, was also obtained and compared with the trends obtained from the theoretical values. The discrepancies in the trends of theoretical and experimental cross-section values of various possible reactions were explained on the basis of the possible errors in experiments and the assumptions of the theoretical model of the TALYS nuclear code

Diagnostic Yield of Closed Pleural Biopsy Using Cope’s Needle in the Diagnosis of Exudative Pleural Effusion

Introduction: The aetiology of pleural effusion may be difficult to diagnose based on the pleural fluid cytology, biochemical and microbiological study. Pleural biopsy using Cope’s needle may help in such cases where definitive diagnosis can not be achieved with the help of cytology. Aim: To make aetiological diagnosis of undiagnosed exudative cases using Closed Pleural Biopsy (CPB) and to determine the diagnostic yield of CPB taken by Cope’s needle in aetiologically confirmed exudative pleural effusion. Materials and Methods: This prospective observation study was conducted in Department of Pulmonary Medicine at Burdwan Medical College and Hospital, Burdwan, West Bengal, India, from April 2021 to March 2022 among 52 patients. Under local anaesthesia, diagnostic and therapeutic thoracocentesis were done. The pleural fluid was sent for complete biochemical, microbiological analysis, and cytology. Later, pleural biopsy was also done using Cope’s pleural biopsy needle. The variables studied were age, gender, pleural fluid cytology, pleural fluid for acid fast bacilli, Gram stain, and culture and pleural biopsy histopathology. Results: Out of 52 patients, 34 (65.4%) were males and 18 (34.6%) were females. The majority of the patients (41, 78.8%) had a right-sided pleural effusion. The mean value of lymphocytes and polymorphs count was 57.7% and 32.7%, respectively. Histopathology showed granulomatous inflammation compatible with tuberculosis in 18 (34.6%) patients, non-specific inflammation in 17 patients (32.7%), and 5 (9.6%) patients as adenocarcinoma. Squamous cell carcinoma was seen in 4 (7.7%), 2 (3.8%) showed undifferentiated carcinoma, while 6 (11.5%) samples had inadequate tissue for opinion. In 6 (11.5%) cases pleural tissue was inadequate to give any opinion. 5 (9.6%) cases showed adenocarcinomas, 2 (3.8%) cases showed squamous cell carcinoma and 4 (7.7%) cases showed undifferentiated carcinoma. The true positives were 18 and 11 for tuberculous and malignant pleural effusion, respectively. The diagnostic yield of pleural biopsy was found to be 75% in case of tubercular pleural effusion and 78.6% for malignant pleural effusion. Conclusion: This study suggests that tuberculosis and malignancy are the two common aetiologies for exudative pleural effusion. Pleural biopsy plays an additional role in histopathological confirmation of aetiologically diagnosed exudative pleural effusion

Calibration and Performance of the REgolith X-Ray Imaging Spectrometer (REXIS) Aboard NASA’s OSIRIS-REx Mission to Bennu

Abstract The REgolith X-ray Imaging Spectrometer (REXIS) instrument on board NASA’s OSIRIS-REx mission to the asteroid Bennu is a Class-D student collaboration experiment designed to detect fluoresced X-rays from the asteroid’s surface to measure elemental abundances. In July and November 2019 REXIS collected ∼615 hours of integrated exposure time of Bennu’s sun-illuminated surface from terminator orbits. As reported in Hoak et al. (Results from the REgolith X-ray Imaging Spectrometer (REXIS) at Bennu, 2021) the REXIS data do not contain a clear signal of X-ray fluorescence from the asteroid, in part due to the low incident solar X-ray flux during periods of observation. To support the evaluation of the upper limits on the detectable X-ray signal that may provide insights for the properties of Bennu’s regolith, we present an overview of the REXIS instrument, its operation, and details of its in-flight calibration on astrophysical X-ray sources. This calibration includes the serendipitous detection of the transient X-ray binary MAXI J0637-430 during Bennu observations, demonstrating the operational success of REXIS at the asteroid. We convey some lessons learned for future X-ray spectroscopy imaging investigations of asteroid surfaces