The Gamma-Ray Imager/Polarimeter for Solar flares (GRIPS) instrument is a balloon-borne telescope designed to study solar- are particle acceleration and transport. We describe GRIPS's first Antarctic long-duration flight in January 2016 and report preliminary calibration and science results. Electron and ion dynamics, particle abundances and the ambient plasma conditions in solar flares can be understood by examining hard X-ray (HXR) and gamma-ray emission (20 keV to 10 MeV). Enhanced imaging, spectroscopy and polarimetry of are emissions in this energy range are needed to study particle acceleration and transport questions. The GRIPS instrument is specifically designed to answer questions including: What causes the spatial separation between energetic electrons producing hard X-rays and energetic ions producing gamma-ray lines? How anisotropic are the relativistic electrons, and why can they dominate in the corona? How do the compositions of accelerated and ambient material vary with space and time, and why? GRIPS's key technological improvements over the current solar state of the art at HXR/gamma-ray energies, the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), include 3D position-sensitive germanium detectors (3D-GeDs) and a single-grid modulation collimator, the multi-pitch rotating modulator (MPRM). The 3D-GeDs have spectral FWHM resolution of a few hundred keV and spatial resolution <1 mm3. For photons that Compton scatter, usually ⪆150 keV, the energy deposition sites can be tracked, providing polarization measurements as well as enhanced background reduction through Compton imaging. Each of GRIPS's detectors has 298 electrode strips read out with ASIC/FPGA electronics. In GRIPS's energy range, indirect imaging methods provide higher resolution than focusing optics or Compton imaging techniques. The MPRM gridimaging system has a single-grid design which provides twice the throughput of a bi-grid imaging system like RHESSI. The grid is composed of 2.5 cm deep tungsten-copper slats, and quasi-continuous FWHM angular coverage from 12.5-162 arcsecs are achieved by varying the slit pitch between 1-13 mm. This angular resolution is capable of imaging the separate magnetic loop footpoint emissions in a variety of are sizes. In comparison, RHESSI's 35-arcsec resolution at similar energies makes the footpoints resolvable in only the largest ares.
A new solar flare spectral component has been found with intensities increasing for larger sub-THz frequencies,
spectrally separated from the well known microwaves component, bringing challenging constraints for interpretation.
Higher THz frequencies observations are needed to understand the nature of the mechanisms occurring in flares. A twofrequency
THz photometer system was developed to observe outside the terrestrial atmosphere on stratospheric balloons
or satellites, or at exceptionally transparent ground stations. 76 mm diameter telescopes were designed to observe the
whole solar disk detecting small relative changes in input temperature caused by flares at localized positions at 3 and 7
THz. Golay cell detectors are preceded by low-pass filters to suppress visible and near IR radiation, band-pass filters,
and choppers. It can detect temperature variations smaller than 1 K with time resolution of a fraction of a second,
corresponding to small burst intensities. The telescopes are being assembled in a thermal controlled box to which a data
conditioning and acquisition unit is coupled. While all observations are stored on board, a telemetry system will forward
solar activity compact data to the ground station. The experiment is planned to fly on board of long-duration
stratospheric balloon flights some time in 2013-2015. One will be coupled to the GRIPS gamma-ray experiment in
cooperation with University of California, Berkeley, USA. One engineering flight will be flown in the USA, and a 2
weeks flight is planned over Antarctica in southern hemisphere summer. Another long duration stratospheric balloon
flight over Russia (one week) is planned in cooperation with the Lebedev Physics Institute, Moscow, in northern
The knowledge of THz continuum spectra is essential to investigate the emission mechanisms by high energy particle
acceleration processes. Technical challenges appear for obtaining selective spectral sensing in the far infrared range to
diagnose radiation produced by solar flare burst emissions measured from space as well as radiation produced by high
energy electrons in laboratory accelerators. Efforts are been carried out intended for the development of solar flare high
cadence radiometers at two THz frequencies to operate outside the terrestrial atmosphere (i.e. at 3 and 7 THz). One
essential requirement is the efficient suppression of radiation in the visible and near infrared. Experimental setups have
been assembled for testing (a) THz transmission of "low-pass" filters: rough surface mirrors; membranes Zitex G110G
and TydexBlack; (b) a fabricated 2.4 THz resonant grid band-pass filter transmission response for polarization and angle
of incidence; (c) radiation response from distinct detectors: adapted commercial microbolometer array using HRFZ-Si
window, pyroelectric module and Golay cell; qualitative detection of solar radiation at a sub-THz frequency has been
tested with a microbolometer array placed at the focus of the 1.5 m reflector for submillimeter waves (SST) at El
Leoncito, Argentina Andes.
The solar submillimeter-wave telescope (SST) is the only one of its kind dedicated to solar continuous observations.
Two radiometers at 0.740 mm (405 GHz), and four at 1.415 mm (212 GHz) are placed in the Cassegrain focal plane of
the 1.5-m dish at El Leoncito high altitude site, San Juan, Argentina. The aperture efficiencies are close to design
predictions: 20% and 35% for 2 and 4 arcminutes beam sizes at 405 and 212 GHz, respectively. The positioner absolute
pointing accuracy is 10 arcseconds. Spectral coverage is complemented by ground-based mid-infrared telescopes
developed for high cadence observations in the continuum 10 micron band (30 THz), using small apertures and room-temperature
microbolometer cameras. Using the system, a new solar burst spectral component was discovered,
exhibiting fluxes increasing for smaller wavelengths, separated from the well known microwave component. Rapid sub-second
pulsations are common for all bursts. The pulsations onset times of appear to be connected to the launch times of
CMEs. Active regions are brighter for shorter submillimeter-waves. Mid-IR bright regions are found closely associated
with calcium plages and magnetic structures near the solar photosphere. Intense and rapid 10 micron brightening was
detected on active centers in association with weak flares. These results raise challenging difficulties for interpretation.
The concept of partially overlapping multiple beams, produced by focal plane arrays in large antennas, has been used successfully at mm-waves to detect instantaneously spatial positions of rapid spikes produced by solar flares. The technique has been used at mm-waves and was recently applied to the Solar Submillimeter-wave Telescope, which operates at 212 and 405 GHz. We present the basic description of the concept and the results obtained. New applications are being considered for shorter submm-IR wavelengths, with the use of focal plane arrays of bolometers, which spatial angular accuracy will strongly depend on the knowledge of the beamshapes of the individual beams produced.