This blog post originated in the 2017 Science Mission Directorate Technology Highlights Report (33 MB PDF).Technology Development
NASA is developing a new type of detector that will provide insight into the formation and structure of the universe. Many of the radiative and mechanical interactions that shape the interstellar medium of galaxies and drive galactic evolution (e.g., shock waves from stellar winds and jets, supernova explosions, etc.) are best observed in the 4.744 terahertz (THz) spectral region for the oxygen line. Observations of this spectral line have rarely been performed, however, because the 4.744-THz frequency is beyond the reach of most existing local oscillators that operate in heterodyne receivers sensitive enough to make such observations. A NASA-sponsored team at Massachusetts Institute of Technology (MIT) is working to advance technologies that will enable upcoming NASA missions to include receivers that observe this important spectral line.
Heterodyne detection compares the incoming light signal with a reference light from a local oscillator (LO). Key challenges of this project are to increase the LO output power from the currently achievable level of <1 mW to 5 mW, and to increase the operating temperature from a lab-demonstrated ~10 K to ~40 K—a temperature that can be accommodated by a space-based or suborbital observatory. To achieve The large circuit board on the left is a previous ASIC design. The three rectangular segments provide three antenna inputs, supporting four 20-MHz channels, and require approximately 5 W of power. To the right is the new ASIC chip. By adding a few small components, such as connectors, it will provide three antenna inputs, with the equivalent of twelve 40-MHz channels, and require only 1 W of power. (Image Credit: Michael Shaw, GigOptics, Inc.) 12 | 2017 SMD Technology Highlights these objectives, the project team is developing local oscillators based on THz quantum-cascade lasers (QCL), which can pump a seven-element heterodyne receiver array. These local oscillators must emit single-frequency radiation with good spectral purity (narrow linewidth <1 MHz at 4.7 THz), which can only be achieved using Distributed-FeedBack (DFB) grating structures. The team investigated three different DFB structures for potential use in the receiver and selected the best option, which has a unidirectional beam pattern (it only radiates in the forward direction) with high output power levels. A picture of such a structure is shown in the figure below.The figure above shows: (a) an array of 3rd-order DFB lasers gold wire bonded to an electronic chip, (b) a photo of a fabricated array of DFB triplets, (c) scanning electron microscope image of a DFB device showing three periods, and (d) a schematic of a triplet with the corresponding radiation profile. Impact
A receiver array capable of observing the 4.744-THz frequency will provide new and unique insights into the interrelationship of stars and gas in a wide range of galactic and extragalactic environments. NASA plans to deploy receivers using this technology on the upcoming GUSTO mission (Galactic/Extragalactic Ultralong-Duration Balloon Spectroscopic Terahertz Observatory), a long-duration balloon payload targeted for launch in 2021. The technology also has potential applications for the upcoming Single Aperture Far-Infrared Observatory (SAFIR) mission, a large cryogenic space telescope envisioned as a follow-on to the Spitzer Space Telescope and the Herschel Space Observatory. In addition to astrophysics, THz QCLs will be useful in a wide range of applications in areas such as security, biochemical sensing, and biomedical imaging.Future Plans
In the near future, the team will develop flight-ready local oscillators for suborbital missions such as GUSTO. In the long term, the work will involve development of local oscillators for space-based observatories such as SAFIR, which will involve devices with even higher performance requirements.Sponsoring Organization
SMD’s Astrophysics Division sponsors this project via the SAT program by providing funding to PI Dr. Qing Hu at MIT.
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On any given day, Zoubaida Salman instructs a classroom of 15-year-olds at the Sur Baher Girls School in East Jerusalem, where she has served as the science teacher and Environment and Health Coordinator for the past 22 years. One of the most important lessons comes from their backyard: water is scarce and precious in this region.
Water shortages can lead to major sanitation issues at schools, so students have to play an active role in managing it. At Sur Baher, the most significant use of water is for flushing toilets, which stop working if there is not enough water. If the water runs out, school administrators must buy it from the city. In other regions, the schools even close because of water shortages.
A team of scientists with the NASA DEVELOP program is helping address these water shortages by collaborating with a nonprofit called Water Resources Action Project(WRAP). WRAP designs and constructs rainwater harvesting systems for schools in the Middle East to capture rainfall during the five-month rainy season for use later. Selecting a geographically promising area is time-consuming and tedious work though for the small, volunteer-based team. The NASA DEVELOP team is using satellite data to help WRAP more easily identify suitable locations for the rainwater harvesting systems.
The NASA-developed tool helps locate potential areas by looking at the region’s historical satellite data of precipitation, groundwater availability, land elevation, and evapotranspiration (the amount of water evaporating from the leaves of plants and from the land surface).NASA Earth Observatory images by Joshua Stevens, using data courtesy of Vishal Arya and the NASA DEVELOP Program.
The maps above show some of the satellite data used to determine suitable locations. The first image shows precipitation from 2006 to 2016, which has remained fairly constant. The precipitation data came from the Tropical Rainfall Measuring Mission (TRMM) and the Global Precipitation Measurement (GPM) mission and were validated with NOAA’s Global Surface Summary of the Day.
The second set of maps shows groundwater availability as observed by the Gravity Recovery and Climate Experiment (GRACE). Since 2006, the Middle East has experienced a net decrease in groundwater.
“We wanted to incorporate data from NASA’s Earth-observing satellites, specifically on precipitation,” said Vishal Arya, who worked on the project at NASA Langley Research Center. “We looked for a correlation between precipitation and environmental factors that could be used to identify areas that would be good candidates for a rainwater harvesting system.”
The data sets have been combined into an interactive Google Earth interface tool called Precipitation Interface for the Middle East (PrIME). PrIME also includes land elevation data from the Shuttle Radar Topography Mission (SRTM) and evapotranspiration data from the Moderate Resolution Imaging Spectroradiometer(MODIS) on the Terra satellite. The tool also includes school locations.
“NASA has served as an invaluable resource, providing WRAP with a readily available decision-making tool,” said Brendan McGinnis, Executive Director of WRAP. “The satellite data show specific numbers over areas affected with limited rainfall and groundwater, rather than us approximating those measurements.”
Before the PrIME tool, WRAP set up rainwater harvesting systems in ten different schools across the Middle East. Now, WRAP has expanded its efforts into Jordan and Palestine. McGinnis hopes to have similar success as its existing programs. At the Al-Afaq School for Special Education in East Jerusalem, WRAP’s rainwater harvesting system has provided nearly 70 percent of the school’s total water needs. Other schools have depended less on water provided by the city.
“The rainwater harvesting system helped us minimize water consumption from the city, especially in winter, and decreased water bills,” said Salman.
Story by Kasha Patel.
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What's Up for September? Set your sights beyond the solar system, and take a late summertime road-trip along the Milky Way.News Article Type: Homepage ArticlesPublished: Tuesday, September 4, 2018 - 10:10