Jik Lee

MEMS micromirror characterization in space environments

This paper describes MEMS micromirror characterization in space environments associated with our space applications in earth observation from the International Space Station and earths orbit satellite. The performance of the micromirror was tested for shock and vibration, stiction, outgassing from depressurization and heating, and electrostatic charging effects. We demonstrated that there is no degradation of the micromirror performance after the space environment tests. A test bed instrument equipped with the micromirrors was delivered and tested in the ISS. The results demonstrate that the proposed micromirrors are suitable for optical space systems.

Experiment on the Vernov satellite: Transient energetic processes in the Earth’s atmosphere and magnetosphere. Part I: Description of the experiment

The program of physical studies on the Vernov satellite launched on July 8, 2014 into a polar (640 × 830 km) solar-synchronous orbit with an inclination of 98.4° is presented. We described the complex of scientific equipment on this satellite in detail, including multidirectional gamma-ray detectors, electron spectrometers, red and ultra-violet detectors, and wave probes. The experiment on the Vernov satellite is mainly aimed at a comprehensive study of the processes of generation of transient phenomena in the optical and gamma-ray ranges in the Earth’s atmosphere (such as high-altitude breakdown on runaway relativistic electrons), the study of the action on the atmosphere of electrons precipitated from the radiation belts, and low- and high-frequency electromagnetic waves of both space and atmospheric origin.

Design and Fabrication of Detector Module for UFFO Burst Alert & Trigger Telescope

The Ultra-Fast Flash Observatory (UFFO) pathfinder is a space mission devoted to the measurement of Gamma-Ray Bursts (GRBs), especially their early light curves which will give crucial information on the progenitor stars and central engines of the GRBs. It consists of two instruments: the UFFO Burst Alert & Trigger telescope (UBAT) for the detection of GRB locations and the Slewing Mirror Telescope (SMT) for the UV/optical afterglow observations, upon triggering by UBAT. The UBAT employs a coded-mask γ/X-ray camera with a wide field of view (FOV), and is comprised of three parts: a coded mask, a hopper, and a detector module (DM). The UBAT DM consists of a LYSO scintillator crystal array, multi-anode photo multipliers, and analog and digital readout electron- ics. We present here the design and fabrication of the UBAT DM, as well as its preliminary test results.

The UFFO (Ultra Fast Flash Observatory) Pathfinder: Science and Mission

Hundreds of gamma-ray burst (GRB) optical light curves have been measured since the discovery of opti- cal afterglows. However, even after nearly 7 years of operation of the Swift Observatory, only a handful of measure- ments have been made soon (within a minute) after the gamma ray signal. This lack of early observations fails to ad- dress burst physics at short time scales associated with prompt emissions and progenitors. Because of this lack of sub- minute data, the characteristics of the rise phase of optical light curve of short-hard type GRB and rapid-rising GRB, which may account for ~30% of all GRB, remain practically unknown. We have developed methods for reaching sub- minute and sub-second timescales in a small spacecraft observatory. Rather than slewing the entire spacecraft to aim the optical instrument at the GRB position, we use rapidly moving mirror to redirect our optical beam. As a first step, we employ motorized slewing mirror telescope (SMT), which can point to the event within 1s, in the UFFO Pathfind- er GRB Telescope onboard the Lomonosov satellite to be launched in Nov. 2011. UFFOs sub-minute measurements of the optical emission of dozens of GRB each year will result in a more rigorous test of current internal shock mod- els, probe the extremes of bulk Lorentz factors, provide the first early and detailed measurements of fast-rise GRB optical light curves, and help verify the prospect of GRB as a new standard candle. We will describe the science and the mission of the current UFFO Pathfinder project, and our plan of a full-scale UFFO-100 as the next step.

The Cosmic Ray Energetics and Mass (CREAM) timing charge detector

H. S. AHN , P. ALLISON , M. G. BAGLIESI , J. J. BEATTY , G. BIGONGIARI , P. BOYLE , J. T. CHILDERS , N. B. CONKLIN , S. COUTU , M. A. DUVERNOIS , O. GANEL , J. H. HAN , J. A. JEON , K. C. KIM , J. K. LEE , M. H. LEE , L. LUTZ , P. MAESTRO , A. MALININE , P. S. MARROCCHESI , S. MINNICK , S. I. MOGNET , S. NAM , S. NUTTER , I. H. PARK , N. H. PARK , E. S. SEO , R. SINA , S. SWORDY , S. WAKELY , J. WU , J. YANG , Y. S. YOON , R. ZEI , S. Y. ZINN . Inst. for Phys. Sci. and Tech., University of Maryland, College Park, MD 20742 USA Dept. of Physics, Ohio State University, Columbus, Ohio 43210, USA Dept. of Physics, University of Siena and INFN, Via Roma 56, 53100 Siena, Italy Enrico Fermi Institute and Dept. of Physics, University of Chicago, Chicago, IL 60637, USA School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA Dept. of Physics, Penn State University, University Park, PA 16802, USA Dept. of Physics, Ewha Womans University, Seoul, 120-750, Republic of Korea Dept. of Physics, Kent State University Tuscarawas, New Philadelphia, OH 44663, USA Dept. of Physics and Geology, Northern Kentucky University, Highland Heights, KY 41099, USA Dept. of Physics, University of Maryland, College Park, MD 20742 USA hsahn@umd.edu

Experiment on the Vernov satellite: Transient energetic processes in the Earth’s atmosphere and magnetosphere. Part II. First results

We present the first experimental results on the observation of optical transients, gamma-ray bursts, relativistic electrons, and electromagnetic waves obtained during the experiment with the RELEC complex of scientific equipment on the Vernov satellite.

Testing and Performance of UFFO Burst Alert & Trigger Telescope

The Ultra-Fast Flash Observatory pathfinder (UFFO-p) is a new space mission dedicated to detect Gamma-Ray Bursts (GRBs) and rapidly follow their afterglows in order to provide early optical/ultraviolet measurements. A GRB location is determined in a few seconds by the UFFO Burst Alert & Trigger telescope (UBAT) employing the coded mask imaging technique and the detector combination of Yttrium Oxyorthosilicate (YSO) scintillating crystals and multi-anode photomultiplier tubes. The results of the laboratory tests of UBATs functionality and performance are described in this article. The detector setting, the pixel-to-pixel response to X-rays of different energies, the imaging capability for <50 keV X-rays, the localization accuracy measurements, and the combined test with the Block for X-ray and Gamma-Radiation Detection (BDRG) scintillator detector to check the efficiency of UBAT are all described. The UBAT instrument has been assembled and integrated with other equipment on UFFO-p and should be launched on board the Lomonosov satellite in late-2015.

Precision measurement technique of photon detection efficiency of Silicon photomultiplier

Silicon photomultiplier (SiPM) is the next generation sensor that is available for single photon counting. We measured the photon detection efficiency (PDE) for the SiPM in the 400 to 800 nm range and over bias voltage up to 4V using photon counting method. The experimental setup consists of multi-wavelength LEDs, a monochromator, two 2-inch integrating spheres, a NIST calibrated reference photodiode and 1×1mm SiPM (1600 micro-pixel). We use the two integrating spheres system to measure PDE measurement. The advantage of this system that we can control light intensity to match dynamic range between the reference photodiode and the SiPM in low light condition. We also calculate precisely the irradiance on the SiPM through the ray-tracing simulation of the experimental setup. We present the results of the PDE measurement as well as the measurement technique.

Boron And Carbon Cosmic rays in the Upper Stratosphere (BACCUS)

The balloon-borne BACCUS experiment measures directly the elemental spectra of cosmic-ray nuclei from protons to Fe over the energy range ~10^12 to 10^15 eV. It focuses on the energy dependence of secondary to primary ratios (e.g. B/C) to investigate cosmic-ray propagation history. BACCUS consists of redundant and complementary particle detectors including the Timing Charge Detector (TCD), Transition Radiation Detector (TRD), Cherenkov Detector (CD), Silicon Charge Detector (SCD), and Calorimeter (CAL). The TCD measures the light yield produced by the particle in plastic scintillator. The TRD provides energy measurements of incident 3 ≤ Z ≤ 26 nuclei in the 102 – 105 Lorentz factor range. The CD responds only to particles with velocity exceeding the velocity of light in the plastic. It allows BACCUS to reject the abundant low energy cosmic rays present in the polar region. The CAL is used to determine the particle’s energy for all nuclei for 1 ≤ Z ≤ 26. With the SCD based on pixellation, in addition to the TCD based on timing, and the CD, the BACCUS instrument implements virtually all possible techniques to minimize the effect of backscatter on charge measurements in the presence of a large particle shower in the CAL. The 30 day flight was carried out successfully over Antarctica in 2016 from Nov. 28 to Dec. 28. The integration test, and performance of instruments will be presented.

Performance of the BACCUS Transition Radiation Detector

The Boron And Carbon Cosmic rays in the Upper Stratosphere (BACCUS) balloon-borne exper- iment flew for 30 days over Antarctica in December 2016. It is the successor of the CREAM balloon program in Antarctica which recorded a total cumulative exposure of 161 days. BAC- CUS is primarily aimed to measure cosmic-ray boron and carbon fluxes at the highest energies reachable with a balloon or satellite experiment, in order to provide essential information for a better understanding of cosmic-ray propagation in the Galaxy. The payload is made of multiple particle physics detectors which measure the charge up to Z=26 and energy of incident particles from a few hundred GeV to a few PeV. The newly designed Transition Radiation Detector (TRD) measures signals that are a function of the charge and Lorentz factor. In April 2016, BACCUS was taken to CERN in its flight configuration to characterize its detectors’ response to beams of electrons and pions. The performance of the TRD using beam test data are reported in this paper.