FIREBIRD-II is a National Science Foundation funded CubeSat mission designed to study the scale size and energy spectrum of relativistic electron microbursts. The mission consists of two identical 1.5 U CubeSats in a low earth polar orbit, each with two solid state detectors that differ only in the size of their geometric factors and fields of view. Having two spacecraft in close orbit allows the scale size of microbursts to be investigated through the intra-spacecraft separation when microbursts are observed simultaneously on each unit. Each detector returns high cadence (10 s of ms) measurements of the electron population from 200 keV to >1 MeV across six energy channels. The energy channels were selected to fill a gap in the observations of the Heavy Ion Large Telescope instrument on the Solar, Anomalous, and Magnetospheric Particle Explorer. FIREBIRD-II has been in orbit for 5 years and continues to return high quality data. After the first month in orbit, the spacecraft had separated beyond the expected scale size of microbursts, so the focus has shifted toward conjunctions with other magnetospheric missions. FIREBIRD-II has addressed all of its primary science objectives, and its long lifetime and focus on conjunctions has enabled additional science beyond the scope of the original mission. This paper presents a brief history of the FIREBIRD mission's science goals, followed by a description of the instrument and spacecraft. The data products are then discussed along with some caveats necessary for proper use of the data.

The Interface Region Imaging Spectrograph (IRIS) small explorer spacecraft provides simultaneous spectra and images of the photosphere, chromosphere, transition region, and corona with 0.33-0.4 arcsec spatial resolution, 2 s temporal resolution and 1 km/s velocity resolution over a field-of-view of up to 175 arcsec x 175 arcsec. IRIS was launched into a Sun-synchronous orbit on 27 June 2013 using a Pegasus-XL rocket and consists of a 19-cm UV telescope that feeds a slit-based dual-bandpass imaging spectrograph. IRIS obtains spectra in passbands from 1332-1358, 1389-1407 and 2783-2834 Angstrom including bright spectral lines formed in the chromosphere (Mg II h 2803 Angstrom and Mg II k 2796 Angstrom) and transition region (C II 1334/1335 Angstrom and Si IV 1394/1403 Angstrom). Slit-jaw images in four different passbands (C II 1330, Si IV 1400, Mg II k 2796 and Mg II wing 2830 Angstrom) can be taken simultaneously with spectral rasters that sample regions up to 130 arcsec x 175 arcsec at a variety of spatial samplings (from 0.33 arcsec and up). IRIS is sensitive to emission from plasma at temperatures between 5000 K and 10 MK and will advance our understanding of the flow of mass and energy through an interface region, formed by the chromosphere and transition region, between the photosphere and corona. This highly structured and dynamic region not only acts as the conduit of all mass and energy feeding into the corona and solar wind, it also requires an order of magnitude more energy to heat than the corona and solar wind combined. The IRIS investigation includes a strong numerical modeling component based on advanced radiative-MHD codes to facilitate interpretation of observations of this complex region. Approximately eight Gbytes of data (after compression) are acquired by IRIS each day and made available for unrestricted use within a few days of the observation.

Focused Investigations of Relativistic Electron Burst Intensity, Range, and Dynamics (FIREBIRD), a space weather-targeted and goal-directed mission supported by the U.S. National Science Foundation, will launch into a high-inclination, low-Earth orbit in October 2013 as a secondary payload under NASA's Educational Launch of Nanosatellites program. FIREBIRD is a dual CubeSat mission that is designed to resolve the spatial scale size and energy dependence of electron microbursts from the Van Allen radiation belts. The FIREBIRD mission embodies the CubeSat ideal: high scientific return provided at low cost through focused and novel investigation of an unexplored yet important phenomenon in a region easily accessed by nanosatellites. FIREBIRD provides a valuable opportunity for students to be involved in multiple aspects of an active space mission, its long duration allowing students to experience all phases from initial concept to final implementation and scientific analysis. Right from the beginning, students and young professionals at the University of New Hampshire and Montana State University played key roles in the development of FIREBIRD, in collaboration with senior scientists at The Aerospace Corporation and Los Alamos National Laboratory. Relativistic electron microbursts appear as short durations of intense electron precipitation measured by particle detectors on low-altitude spacecraft, seen episodically when their orbits cross magnetic flux tubes that thread the outer radiation belt [Lorentzen, 2001a, 2001b]. Previous spacecraft missions (e.g., SAMPEX) have quantified important aspects of microburst properties (e.g., occurrence probabilities); however, other crucial properties (e.g., spatial scale) remain elusive owing to the space-time ambiguity inherent to single-spacecraft missions. While microbursts are thought to be a significant loss mechanism for relativistic electrons [O'Brien et al., 2004], they remain poorly understood, thus rendering space weather predictive models of Earth's radiation belts incomplete. The so-called “killer” electrons in the radiation belt can produce deep dielectric discharging in spacecraft components, a significant concern for satellite health and operations. FIREBIRD's two-point, focused observations at low altitudes address three fundamental scientific questions with important space weather implications: (1) What is the spatial scale size of an individual microburst? (2) What is the energy dependence of an individual microburst? (3) How much total electron loss from the radiation belts do microbursts produce globally? FIREBIRD's unique microburst observations will significantly advance understanding of relativistic electron precipitation loss from the outer zone radiation belt, which, in turn, will provide insight not only into the current state of the belt but also potentially into future states. Each FIREBIRD CubeSat (see Figure 1) possesses two solid-state detector charged particle sensors with different geometric factors optimized to cover electron measurements over the energy range from 0.25 to ~1 MeV in six differential energy channels. The detectors are read out by a custom application-specific integrated circuit (ASIC), designed by The Aerospace Corporation, called the Dual Amplifier Pulse Peak Energy Rundown ASIC. Onboard memory (~2 gigabytes) stores fast sample (~20 milliseconds) observations needed to resolve spatial structure; survey observations identify times of interest to download the highest temporal resolution data within the limited telemetry stream (~4 megabytes per day). While all data from the instruments are saved on board for 2 weeks, FIREBIRD telemeters a reduced event identification data product to the ground each day in order to select particular intervals with microbursts to download for scientific analysis. The two FIREBIRD CubeSat packages will be delivered to California Polytechnic State University, San Luis Obispo, in April 2013 for integration into the Poly Picosatellite Orbital Deployer [Puig-suari et al., 2001]. Both undergraduate and graduate students will analyze FIREBIRD data as part of their academic experience. After a short data validation period, all data will be available for public use. The mission is highly complementary to large flagship strategic space missions such as the recently launched Radiation Belt Storm Probes mission [Mauk et al., 2012] and the upcoming BARREL balloon mission [Millan and the BARREL Team, 2011]. Acknowledgments. The National Science Foundation supported this work under grants to the University of New Hampshire (grant ATM-1035642) and Montana State University (grant ATM-0838034). H. E. Spence is director of the Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH 03824, USA. E-mail: [email protected]. J. B. Blake is a member of the technical staff at The Aerospace Corporation, El Segundo, CA 90009, USA. A. B. Crew is a graduate student at Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH 03824, USA. S. Driscoll is a graduate research assistant at Space Science and Engineering Laboratory, Department of Physics, Montana State University, Bozeman, MT 59717, USA. D. M. Klumpar is director of the Space Science and Engineering Laboratory, Department of Physics, Montana State University, Bozeman, MT 59717, USA. B. A. Larsen is a technical staff member at Space Science and Applications, Los Alamos National Laboratory, Los Alamos, NM 87545, USA. J. Legere is a research project engineer at the Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH 03824, USA. S. Longworth is a senior research project engineer at Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH 03824, USA. E. Mosleh is a research engineer at Space Science and Engineering Laboratory, Department of Physics, Montana State University, Bozeman, MT 59717, USA. T. P. O'Brien is a research scientist at The Aerospace Corporation, El Segundo, CA 90009, USA. S. Smith is a project manager at the Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH 03824, USA. L. Springer is senior research engineer and program manager at Space Science and Engineering Laboratory, Department of Physics, Montana State University, Bozeman, MT 59717, USA. M. Widholm is a research project engineer at the Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH 03824, USA.

SOHO offers an unprecedented opportunity to probe the interior of a star with the techniques of helioseismology. Continuous distortion-free observations of the Sun will provide unique measurements of its internal structure and dynamics. The MDI instrument provides the capability to obtain observations with very high spatial resolution and high precision at all times, with statistical errors well below the expected solar noise background at all frequencies. The real limitation will be gaining a sufficient understanding of the systematic error sources with characteristic periods longer than several hours.