¾«Æ·SMÔÚÏßӰƬ

From NRAO eNews:  The NRAO Central Development Laboratory (CDL) is assisting with the development of the Dark Ages Polarimeter Pathfinder (DAPPER), a lunar-orbiting spacecraft concept designed to measure the spectrum of highly-redshifted hydrogen emitted during Cosmic Dawn, the epoch of initial star formation in the evolution of the Universe. The challenge of this measurement in the 20-100 MHz frequency range is the rather weak, isotropic nature of the hydrogen radiation in the presence of strong foreground emission that is many orders of magnitude brighter.  DAPPER has several advantages over ground-based instruments in that it is above the signal distorting effects of the ionosphere, clear of local environmental effects that are difficult to model, and will acquire sky data during the time in its orbit when the Moon shields the spacecraft from Earth-based radio interference. It also incorporates a novel dynamic polarimetry technique, developed by Richard Bradley’s group at the CDL, to help separate the foreground spectrum from that of Cosmic Dawn hydrogen. 

NASA Ames Research Center is hosting the DAPPER project, led by PI Jack Burns (University of Colorado, Boulder) and Co-Is Richard Bradley (NRAO CDL) and Stuart Bale (Berkeley Space Sciences Laboratory). The purpose of our current two-year program is to advance the Technology Readiness Level (TRL) of the instrumentation to TRL 6 – eliminating the technological risks of the mission. The NRAO CDL will lead the development of the 60-100 MHz antenna, receiver / calibration modules, signal processing algorithms, and the ground-based engineering prototype that will be deployed at the Green Bank Observatory (GBO). The Space Sciences Laboratory will perform the space environmental tests on our prototype hardware and migrate the software to an FPGA-based platform. Data from the GBO deployment will be used by the University of Colorado group to evaluate and advance the capabilities of their machine-learning-based data analysis pipeline for DAPPER.