The origin of the cosmic diffuse gamma-ray (CDG) background in the 0.3 – 30 MeV energy range is a mystery that has persisted for over 40 years. The Mini Astrophysical MeV Background Observatory (MAMBO) is a CubeSat mission concept motivated by the fact that, since the MeV CDG is relatively bright, only a small detector is required to make highquality measurements of it. Indeed, the sensitivity of space-based gamma-ray instruments to the CDG is limited not by size, but by the locally generated instrumental background produced by interactions of energetic particles in spacecraft materials. Comparatively tiny CubeSat platforms provide a uniquely quiet environment relative to previous gamma-ray science missions. The MAMBO mission will provide the best measurements ever made of the MeV CDG spectrum and angular distribution, utilizing two key innovations: 1) low instrumental background on a 12U CubeSat platform; and 2) an innovative shielded spectrometer design that simultaneously measures signal and background. We describe the MAMBO instrument and mission concept in detail, including simulations and laboratory measurements demonstrating the key measurement concept.
The Raytheon Trimodal Imager (TMI) uses coded aperture and Compton imaging technologies as well as the nonimaging
shadow technology to locate an SNM or radiological threat in the presence of background. The coded aperture
imaging is useful for locating and identifying radiological threats as these threats generally emit lower energy gammas
whereas the Compton imaging is useful for SNM threats as in addition to low energy gammas which can be shielded,
SNM threats emit higher energy gammas as well. The shadow imaging technology utilizes the structure of the
instrument and its vehicle as shadow masks for the individual detectors which shadow changes as the vehicle moves
through the environment. Before a radioactive source comes into the fields of view of the imagers it will appear as a
shadow cast on the individual detectors themselves. This gives the operator advanced notice that the instrument is
approaching something that is radiological and on which side of the vehicle it is located. The two nuclear images will be
fused into a combined nuclear image along with isotope ID. This combined image will be further fused with a real-time
image of the locale where the vehicle is passing. A satellite image of the locale will also be made available. This
instrument is being developed for the Standoff Radiation Detection System (SORDS) program being conducted by
Domestic Nuclear Detection Office (DNDO) of the Department of Homeland Security (DHS).
The Advanced Compton Telescope (ACT), the next major step in gamma-ray astronomy, will probe the fires where
chemical elements are formed by enabling high-resolution spectroscopy of nuclear emission from supernova explosions.
During the past two years, our collaboration has been undertaking a NASA mission concept study for ACT. This study
was designed to (1) transform the key scientific objectives into specific instrument requirements, (2) to identify the most
promising technologies to meet those requirements, and (3) to design a viable mission concept for this instrument. We
present the results of this study, including scientific goals and expected performance, mission design, and technology
The most serious terrorist threat we face today may come from
radiological dispersion devices and unsecured nuclear weapons. It is imperative for national security that we develop and implement radiation detection technology capable of locating and tracking nuclear material moving across and within our borders. Many radionuclides emit gamma rays in the 0.2 -- 3 MeV range. Unfortunately, current gamma ray detection technology is inadequate for providing precise and efficient measurements of localized radioactive sources. Common detectors available today suffer from large background rates and have only minimal ability to localize the position of the source without the use of mechanical collimators, which reduces efficiency. Imaging detectors using the Compton scattering process have the potential to provide greatly improved sensitivity through their ability to reject off-source background. We are developing a prototype device to demonstrate the Compton imaging technology. The detector consists of several layers of pixelated
silicon detectors followed by an array of CsI crystals coupled to
photodiodes. Here we present the concept of our detector design and
results from Monte Carlo simulations of our prototype detector.
The next large NASA mission in the field of gamma-ray astronomy, GLAST, is scheduled for launch in 2007. Aside from the main instrument LAT (Large-Area Telescope), a gamma-ray telescope for the energy range between 20 MeV and > 100GeV, a secondary instrument, the GLAST burst monitor (GBM), is foreseen. With this monitor one of
the key scientific objectives of the mission, the determination of the high-energy behaviour of gamma-ray bursts and transients can be ensured. Its task is to increase the detection rate of gamma-ray bursts for the LAT and to extend the energy range to lower energies (from ~10 keV to ~30 MeV). It will provide real-time burst locations over a wide FoV with sufficient accuracy to allow repointing the GLAST spacecraft. Time-resolved spectra of many bursts recorded with LAT and the burst monitor will allow the investigation of the relation between the keV and the MeV-GeV emission from GRBs over unprecedented seven decades of energy. This will help to advance our understanding of the mechanisms by which gamma-rays are generated in gamma-ray bursts