The Ionospheric Connection Explorer (ICON) is a NASA Heliophysics Explorer Mission designed to study the ionosphere. ICON will examine the Earth's upper atmosphere to better understand the relationship between Earth weather and space-weather drivers. ICON will accomplish its science objectives using a suite of 4 instruments, one of which is the Extreme Ultraviolet Spectrograph (EUV). EUV will measure daytime altitude intensity profile and spatial distribution of ionized oxygen emissions (O+ at 83.4 nm and 61.7 nm) on the limb in the thermosphere (100 to 500 km tangent altitude). EUV is a single-optic imaging spectrometer that observes in the extreme ultraviolet region of the spectrum. In this paper, we describe instrumental performance calibration measurement techniques and data analysis for EUV. Various measurements including Lyman-α scattering, instrumental and component efficiency, and field-of-view alignment verification were done in custom high-vacuum ultraviolet calibration facilities. Results from the measurements and analysis will be used to understand the instrument performance during the in-flight calibration and observations after launch.
An imaging spectrometer for observations of the Martian corona and the Martian thermosphere is presented. The corona extends over 10 Martian radii and its measurement requires observations over a very wide field. The spectrometer covers the wavelength region 120-170 nm where this band includes coronal spectral lines of hydrogen Lyman alpha and oxygen, and thermospheric spectral lines from atomic oxygen and carbon and the 4th positive band of CO. Stellar occultation observations will provide atmospheric density measurements. These scientific requirements are fulfilled by an Offner-type spectrometer with a 110 degree instantaneous field of view and no moving mechanisms. Both the spectral and imaging resolution vary across the field, from higher resolution across the planet body, to lower resolution required at the diffuse outer parts of the corona. This Offner-type design has not been previously used in the FUV.
Since it’s public release in 1999, the capabilities of SETI@home have grown rapidly. The continuation of Moore's law has led to personal computers one thousand times faster than those available in 1999, with graphics processing units that can provide processing speeds only seen on supercomputers in the last century. The capabilities of the SETI@home software have increased to better utilize the available processing power. Increases in radio astronomy instrumentation technologies have also led to improvements in the potential data sources for SETI@home. I will describe the evolution of SETI@home, and how it will change in the future to better match the available technologies, in the data sources, the data processing techniques, and the candidate identification process.
We summarize radio and optical SETI programs based at the University of California, Berkeley.
The SEVENDIP optical pulse search looks for ns time scale pulses at visible wavelengths. It utilizes an automated 30
inch telescope, three ultra fast photo multiplier tubes and a coincidence detector. The target list includes F, G, K and M
stars, globular cluster and galaxies.
The ongoing SERENDIP V.v sky survey searches for radio signals at the 300 meter Arecibo Observatory. The currently
installed configuration supports 128 million channels over a 200 MHz bandwidth with ~1.6 Hz spectral resolution.
Frequency stepping allows the spectrometer to cover the full 300MHz band of the Arecibo L-band receivers. The final
configuration will allow data from all 14 receivers in the Arecibo L-band Focal Array to be monitored simultaneously with
over 1.8 billion channels.
SETI@home uses the desktop computers of volunteers to analyze over 160 TB of data at taken at Arecibo. Over
6 million volunteers have run SETI@home during its 10 year history. The SETI@home sky survey is 10 times more
sensitive than SERENDIP V.v but it covers only a 2.5 MHz band, centered on 1420 MHz. SETI@home searches a
much wider parameter space, including 14 octaves of signal bandwidth and 15 octaves of pulse period with Doppler drift
corrections from -100 Hz/s to +100 Hz/s. SETI@home is being expanded to analyze data collected during observations of
Kepler objects of interest in May 2011.
The Astropulse project is the first SETI search for μs time scale pulses in the radio spectrum. Because short pulses are
dispersed by the interstellar medium, and the amount of dispersion is unknown, Astropulse must search through 30,000
possible dispersions. Substantial computing power is required to conduct this search, so the project uses volunteers and
their personal computers to carry out the computation (using distributed computing similar to SETI@home).
Keywords: radio instrumentation, FPGA spectrometers, SETI, optical SETI, Search for Extraterrestrial Intelligence, volunteer
computing, radio transients, optical transients.
The SPEAR (Spectroscopy of Plasma Evolution from Astrophysical Radiation) mission to map the far ultraviolet sky uses micro-channel plate (MCP) detectors with a crossed delay line anode to record photon arrival events. SPEAR has two MCP detectors, each with a ~25mm x 25 mm active area. The unconventional anode design allows for the use of a single set of position encoding electronics for both detector fields. The centroid position of the charge cloud, generated by the photon-stimulated MCP, is determined by measuring the arrival times at both ends of the anode following amplification and external delay. The temporal response of the detector electronics system determines the readout's positional resolution for the charge centroid. High temporal resolution (< 35ps x 75ps FWHM) and low power consumption (<6W) are required for the SPEAR detector electronics system. We describe the development and performance of the detector electronics system for the SPEAR mission.
The evolution of hot interstellar medium (ISM) in galaxies is fundamental to the evolution of our cosmos. The Spectroscopy of Plasma Evolution from Astrophysical Radiation (SPEAR) mission will study the hot ISM, providing pointed observations and the first all-sky spectral maps in the Far (FUV) Ultraviolet. The FUV bandpass contains the primary cooling lines of abundant elements in a variety of ionization states. SPEAR's broad bandpass (λλ 900 - 1750 Å), spectral resolution (λ/δλ ~ 700) and imaging resolution (5' - 10') has been chosen to determine independently the quantity, temperature, depletion, and ionization of hot galactic gas. These SPEAR data will allow us to study the hot ISM on both large and small scales and to discriminate among models of the large-scale creation, distribution, and evolution of hot gas in the Galactic disk and halo.
The SPEAR micro-satellite payload consists of dual imaging spectrographs optimized for detection of the faint, diffuse FUV (900-1750 Å) radiation emitted from interstellar gas. The instrument provides spectral resolution, R~750, and long slit imaging of <10' over a large (8°x5') field of view. We enhance the sensitivity by using shutters and filters for removal of background noise. Each spectrograph channel uses identically figured optics: a parabolic-cylinder entrance mirror and a constant-ruled ellipsoidal grating. Two microchannel plate photon-counting detectors share a single delay-line encoding system. A payload electronics system conditions data and controls the instrument. We will describe the design and predicted performance of the SPEAR instrument system and its elements.
We describe the development of optics for the SPEAR space-mission
to map the far ultraviolet (900-1750 Å) sky. The SPEAR
spectrometers contain unusual reflective optics to optimize
sensitivity to diffuse emission. We describe the manufacture, test
and performance of the collecting mirrors: Pyrex parabolic
cylinders with a 90 degree off-axis angle. We also describe the
development of the diffraction gratings: ellipses of rotation that
are holographically-ruled with constant spacing and blazed with
We present results from two radio and two optical SETI programs at the University of California, Berkeley: The SERENDIP IV sky survey searches for narrow band radio signals at the 305 meter Arecibo Observatory in Puerto Rico. The program uses a 168 million channel spectrum analyser, running in 'piggyback' mode, using a dedicated receiver to take data 24 hours a day, year round. SETIhome is Berkeley's most recent SETI project. SETIhome uses desktop computers of over a million volunteers to analyse 40 Terabytes of data from Arecibo Observatory. SETIhome is the largest supercomputer on the planet, currently averaging 20 Teraflops. The SEVENDIP optical program searches for nS timescale pulses at visible wavelengths. The target list includes nearby F,G,K and M stars, plus a few globular cluster and galaxies. The pulse search utilizes Berkeley's 30 inch automated telescope at Leuschner Observatory. Another Berkeley optical SETI program searches for narrow band coherent signals in high resolution stellar spectra taken by Marcy and his colleagues as part of their on-going search for planets at Lick, Keck, and the Anglo-Australian observatories.
Far-ultraviolet IMaging Spectrograph (FIMS) is a far ultraviolet diffuse imaging spectrometer which will be launched in 2002 as the main payload of KAISTSAT-4. We have designed the optics for observing diffuse emission sources by employing an off-axis parabolic cylinder mirror in front of a slit which guides lights to a diffraction grating. The reflective diffraction grating is an ellipse of rotation providing angular resolution. We describe our plan to measure the off-axis parabolic mirror and our initial experiments to establish the measurement technique. To assist manufacture of the off-axis parabolic cylinder, a cylindrical wavefront generated using computer generated hologram (CGH) will be used during the polishing to check errors in surface profile using the Fizeau interferometer.