Recent solar flare observations have shown the existence of a spectral component exhibiting fluxes increasing with frequency in the sub-THz spectrum simultaneously with the well known spectral component peaking at microwaves bringing challenging constraints for interpretation. This double spectral feature cannot be well explained by existing models. One possibility is to associate the high frequency emissions to incoherent synchrotron radiation (ISR) produced by flare accelerated beams of high energy electrons with intensity peaking at THz frequencies. Certain wave-particle instabilities may set in the electron beam, giving rise to bunching of the electrons which could radiate powerful broadband coherent synchrotron radiation (CSR) in the microwave spectrum peaking at wavelengths comparable to the size of the bunching. Although this CSR process has been observed in laboratory accelerators, only now has its association to solar flare physics been explored. Simulations have shown that the mechanism may be extremely efficient and highly localized in solar flares. To demonstrate the high energy ISR emission in flares it is necessary to measure the complete continuum spectra at higher THz frequencies, outside the terrestrial atmosphere. A THz telescope has been developed with a 75 mm primary reflector with rough surface to diffuse part of the incoming visible and near IR radiation. Golay cell detectors are preceded by low-pass membranes and band-pass metal mesh resonant filters tuned at 3 and 7 THz. © 2011 IEEE. Shimabukuro, F.I., The observation of 3.3-mm bursts and their correlation with soft X-ray bursts (1970) Solar Phys., 15, pp. 424-432Akabane, K., A flare-associated thermal burst in the mm-wave region (1973) Solar Phys., 33, pp. 431-437Zirin, H., Tanaka, K., The flares of August 1972 (1973) Solar Phys., 32, pp. 173-207Kaufmann, P., Raulin, J.-P., Gimenez, D.C.C.G., Levato, H., Gary, D.E., Costa, J.E.R., Marun, A., Correia, E., A new solar burst spectral component emitting only in the terahertz range (2004) Astrophysical Journal, 603 (2 II), pp. L121-L124. , DOI 10.1086/383186Kaufmann, P., Sub-terahertz, Microwaves and High Energy Emissions during the 6 December 2006 Flare, at 18:40 UT (2009) Solar Phys., 255, pp. 131-142Silva, A.V.R., Evidence that Synchrotron Emission from Nonthermal Electrons Produces the Increasing Submillimeter Spectral Component in Solar Flares (2007) Solar Phys., 245, pp. 311-326Trottet, G., Radio Submillimeter and ã-Ray Observations of the 2003 October 28 Solar Flare (2008) Astrophys. J., 577, pp. 509-514Sakai, J.I., Simulating the emission of electromagnetic waves in the terahertz range by relativistic electron beams (2006) Astron.Astrophys., 457, p. 313Sakai, J.I., Nagasugi, Y., Emission of electromagnetic waves by proton beams in solar plasmas (2007) Astron.Astrophys., 474, pp. L33Kaufmann, P., A Synchrotron/Inverse Compton Interpretation of a Solar Burst Producing Fast Pulses at 3mm Wavelength and Hard X-Rays (1986) Astron.Astrophys., 157, pp. 11-18Fleishman, G.F., Kontar, E.P., Sub-THz radiation mechanisms in solar flares (2010) Astrophys. J., 709, pp. L127-L132Williams, G.P., FAR-IR/THz radiation from the Jefferson Laboratory, energy recovered linac, free electron laser (2002) Rev. Sci. Instrum., 73, pp. 1461-1463Kaufmann, P., Raulin, J.-P., Can microbunch instability on solar flare accelerated electron beams account for bright broadband coherent synchrotron microwaves? (2006) Phys.Plasmas, 13, p. 070701Klopf, J.M., Kaufmann, P., Raulin, J.-P., Examination of broadband coherent synchrotron radiation to describe THz and sub-THz solar flare spectral emissions (2010) Bulletin American Astronomical Society, 42, p. 905Kaufmann, P., Selective Spectral Detection of Continuum Terahertz Radiation Proc. SPIE 7741, San Diego, CA, 28 June-2 July, 2010, , paper 7741-77Melo, A.M., Metal mesh resonant filters for terahertz frequencies (2008) Applied Optics, 47, pp. 6064-6069Fernandes, L.O.T., Photometry of THz Radiation Using Golay Cell Detector, , this XXX URSI GAKaufmann, P., Search for Continuum Solar Flare Radiation in the Terahertz Range Proc. of IRMMWTHz 2010 Conference, Rome, Italy, 5-10 September, 2010Shih, A., The Gamma-Ray Imager/Polarimeter for Solar Flares (GRIPS) (2008) American Geophysical Union, Fall Meeting, , abstract SM11B-1602