Development of the ARICA-2 Satellite Using Spresense as an Onboard Computer

Gamma-ray bursts (GRBs) are transient astronomical phenomena that emit enormous amounts of energy in electromagnetic waves, mainly in the gamma-ray range, for several seconds to tens of seconds. GRB observations are challenging because of the difficulty in predicting the location and time of occurrence and its extremely short duration. Therefore, it is necessary to notify about the discovery in space and to conduct follow-up observations by researchers. The AGU Remote Innovative CubeSat Alert system-2 (ARICA-2) has been developed to demonstrate a new alert system using commercial satellite network services. ARICA-2 uses SONY’s Spresense as its onboard computer (OBC). We manufactured the special board to attach two Spresenses as a redundancy of the OBC system. We will present the system development of ARICA-2 using Spresense

Power System Development of the AGU Remote Innovative CubeSat Alert System -2 – ARICA-2

We present the power system development of the 2U CubeSat, AGU Remote Innovative CubeSat Alert system -2(ARICA-2). The main goal of the ARICA-2 project is to demonstrate the real-time alert system of transient astronomical sources using commercial satellite network devices. 1U CubeSat ARICA was launched in November 2021. However, we have not been able to send and receive the data at this point. Therefore, we started developing 2U CubeSat ARICA-2, which is an improved version of ARICA, in April 2022. One of the possible causes of the communication problem of ARICA is the power system, such as a negative power budget or a failure in the installation of the inhibit switches. ARICA-2 is upsized from 1U to 2U to ensure a sufficient power generation and is equipped with improved inhibit switches. The calculation of power consumption and simulation of power supply on orbit have been finished. We confirmed the performance of our Electric Power System (EPS) and the health of the installed batteries. We are currently in the EM development phase with the goal of launching in Japanese fiscal year 2024

Overview and Status of AGU Remote Innovative Cubesat Alert System-2 on 2023

We present the overview of the 2U CubeSat, AGU Remote Innovative Cubesat Alert system - 2 (ARICA-2). ARICA-2 was selected as a feasibility study phase of the JAXA-Small Satellite Rush Program (JAXA-SMASH) and the JAXA Innovative Satellite Technology Demonstration-4 project in 2022. The main goal of ARICA-2 is to demonstrate the real-time alert system of transient astronomical sources, such as gamma-ray bursts, using commercial satellite network services. The first 1U CubeSat ARICA, which had the same mission goal as ARICA-2, was successfully launched in 2021 by the JAXA’s Epsilon rocket No.5. However, communication with ARICA has yet to be established due to severe hardware issues. Therefore, ARICA-2 is the re-challenging mission of ARICA. ARICA-2 has several different features compared to ARICA. First, a transceiver using amateur radio frequency is added to the commercial satellite network devices to communicate directly from the ground. Second, ARICA-2 uses Sony’s low-power board Spresense as an onboard computer. Third, the attitude control system using magnetorquer is installed to establish better communication with the commercial network satellites. Fourth, the size of a gamma-ray detector is 70 mm x 70 mm x 10 mm, which is larger by a factor of 200 in volume compared to ARICA, to enhance the detection rate of gamma-ray bursts. We plan to develop the engineering model (EM) in 2023 and perform thermal vacuum and vibration tests on the EM. We report the current status and a prospect of ARICA-2

Estimating Discrete Markov Models From Various Incomplete Data Schemes

The parameters of a discrete stationary Markov model are transition probabilities between states. Traditionally, data consist in sequences of observed states for a given number of individuals over the whole observation period. In such a case, the estimation of transition probabilities is straightforwardly made by counting one-step moves from a given state to another. In many real-life problems, however, the inference is much more difficult as state sequences are not fully observed, namely the state of each individual is known only for some given values of the time variable. A review of the problem is given, focusing on Monte Carlo Markov Chain (MCMC) algorithms to perform Bayesian inference and evaluate posterior distributions of the transition probabilities in this missing-data framework. Leaning on the dependence between the rows of the transition matrix, an adaptive MCMC mechanism accelerating the classical Metropolis-Hastings algorithm is then proposed and empirically studied.Comment: 26 pages - preprint accepted in 20th February 2012 for publication in Computational Statistics and Data Analysis (please cite the journal's paper

Verification of 11C scanning irradiation with offline PET

A scheme for offline PET measurement of 11C beam irradiation field has been developed in order to verify a three-dimensionally conformal irradiation field for particle radiotherapy. With use of positron emitter beams such as 11C, the verification of therapeutic irradiation can be directly accomplished by observing annihilation-pair gamma rays from the stopping point in the patient. One of the features of 11C therapeutic beam is the large number of the annihilation gamma ray observed at the range of the incident beam. The half-life of 11C is 20.39 min, which is appropriate for measurements using offline positron emission tomography (PET).The experiment to simulate the treatment irradiation and offline PET verification was accomplished with PMMA phantom. The concave-shaped irradiation field was optimised with 1 Gy in uniform phantom. The dose distribution of the concave field is confirmed with multi-channel ionization chamber and the water column in advance. To reduce the set up error at the PET gantry, the platform on the couch of PET is prepared and the reference position of the platform is fixed using the 22Na point source. After the irradiation with 11C (345 MeV/n) by HIMAC scanning system, the phantom is set on the platform in the PET gantry and measured for an hour. In this conference, the results of the PET verification of 11C irradiation field will be presented.40th　PTCO

Dose Distribution of Heavy-ion Scanning Irradiationfor Simulated for Moving Target

Objective:Heavy ion radiotherapy is characterized its excellent physical dose localization and the biological effectiveness because of its high linear energy transfer (LET). The scanning irradiation of heavy ion, which is the highly conformal techniques, is more sensitive to motion effects. The consequence can be under-dosage of the target volume or over-dosage of critical structures. The effectiveness of scanning irradiation with the respiratory-gated techniques for the moving target is evaluated in this study.Material and Methods:The scanning irradiation using carbon ions is planed to the target contours on a set of 3D CT images. They are converted to the water equivalent depth coordinate and the prescribed dose is set in and around the target region. The Bragg peaks of beams are arranged in the water equivalent space, and the weight of each beam spot is optimized to meet the condition of the prescribed dose. From the optimized beam arrangement and the weight, the planned dose distribution is calculated and displayed on the axial, sagittal, or coronal multiplanar reconstruction CT image. The motion models are constructed based on a set of sequential 3D CT volume (4D CT) data of various clinical cases, such as lung and liver tumor. And the dose distribution simulated for the moving target is evaluated with this model. Results:The scanning-irradiated dose distribution is simulated for the clinical targets based on the motion analysis of tumor. The motion of tumor is analyzed by the direction, distance, speed and variation of density. Especially for the heavy-ion radiotherapy, the density through beam path is crucial because it affects strongly on the dose coverage around the distal end of the tumor. For some clinical moving models, the dose uniformities in planning target volume and the outer dosage on normal tissue are estimated with the timing for respiration. The quantitative analysis with the scanning parameters such as beam size, arrangement and scanning speed, is on going.Conclusion:This simulation of scanning irradiation enables the clinical evaluation of the dose distribution for the moving target. The effect on dose uniformity is estimated and the engineering requirements for the scanning devices can be examined to the tumor on moving target.Third International Conference on Translational Research and Pre-Clinical Stratgies in Radiation Oncolog