Eric J. Korpela

• Ph.D.
• Research Astronomer at University of California, Berkeley

The two-year prime mission of the NASA Ionospheric Connection Explorer (ICON) is complete. The baseline operational and scientific objectives have been met and exceeded, as detailed in this report. In October of 2019, ICON was launched into an orbit that provides its instruments the capability to deliver near-continuous measurements of the densest...

We present in-flight performance measurements of the Ionospheric Connection Explorer EUV spectrometer, ICON EUV, a wide field (17∘×12∘\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \beg...

The NASA Ionospheric Connection Explorer Extreme Ultraviolet spectrograph, ICON EUV, images one-dimensional altitude profiles of the daytime extreme-ultraviolet (EUV) airglow between 54-88 nm. This spectral range contains several OII emission features derived from the photoionization of atomic oxygen by solar EUV. The primary target of the ICON EUV...

We provide the first comparison of the ICON-EUV O⁺ density profile with radio wave datasets coming from GNSS radio-occultation, ionosondes and incoherent scatter radar. The peak density and height deduced from those different observation techniques are compared. It is found that the EUV-deduced peak density is smaller than that from other technique...

As a major approach to looking for life beyond the Earth, the search for extraterrestrial intelligence (SETI) is committed to searching for technosignatures such as engineered radio signals that are indicative of technologically capable life. In this paper, we report a targeted SETI campaign employing an observation strategy named multibeam coincid...

Plain Language Summary The ionosphere is a region of near‐Earth space made up of plasma. NASA's Ionospheric Connection Explorer (ICON) mission seeks explore the factors influencing formation of the ionosphere and how it interacts with Earth and its atmosphere. One of the ways ICON does this is by measuring airglow: light released by the air in the...

As a major approach to looking for life beyond the Earth, the search for extraterrestrial intelligence (SETI) is committed to detecting technosignatures such as engineered radio signals that are indicative of technologically capable life. In this paper, we report a targeted SETI campaign employing an observation strategy named multi-beam coincidenc...

New opportunities are being enabled by state‐of‐the‐art instrumentation to search for technosignatures (TS) in time‐series photometric observations. We review existing proposals for detectable TS around extrasolar planets or their parent stars and discuss them in the context of the “axes of merit”. We briefly describe the methods by which such sign...

Are we alone?' The Search for Extra-Terrestrial Intelligence (SETI) aims to answer this profound question. Apart from examining environments in our solar system and detecting biosignatures in exoplanet atmospheres, SETI is another main approach to search for life beyond Earth by detecting technosignatures indicative of extra-terrestrial intelligenc...

Plain Language Summary At high altitude in the atmosphere, mixing of the gas via turbulence becomes less important, and mix of atmospheric species begins to vary with altitude, depending on the mass of the atom or molecule. At these altitudes, the composition of the atmosphere can vary greatly with location and time in a manner not seen in the lowe...

The discovery of ubiquitous habitable extrasolar planets, combined with revolutionary advances in instrumentation and observational capabilities, has ushered in a renaissance in the search for extraterrestrial intelligence (SETI). Large scale SETI activities are now underway at numerous international facilities. The Five-hundred-meter Aperture Sphe...

The discovery of ubiquitous habitable extrasolar planets, combined with revolutionary advances in instrumentation and observational capabilities, has ushered in a renaissance in the search for extra-terrestrial intelligence (SETI). Large scale SETI activities are now underway at numerous international facilities. The Five-hundred-meter Aperture Sph...

The Search for Extraterrestrial Intelligence (SETI) attempts to address the possibility of the presence of technological civilizations beyond the Earth. Benefiting from high sensitivity, large sky coverage, and an innovative feed cabin for China's Five-hundred-meter Aperture Spherical radio Telescope (FAST), we performed SETI's first observations w...

The Search for Extraterrestrial Intelligence (SETI) attempts to address the possibility of the presence of technological civilizations beyond the Earth. Benefiting from high sensitivity, large sky coverage, an innovative feed cabin for China's Five-hundred-meter Aperture Spherical radio Telescope (FAST), we performed the SETI first observations wit...

We analyze the potential transit light curve effects due to a Clarke belt of satellites around an exoplanet. Building on code and analysis from Korpela et al., we refine the transit analysis of Socas-Navarro by incorporating limb-darkening and taking an observer-centered approach to examining residuals. These considerations make Clarke exobelt dete...

We analyze the potential transit light curve effects due to a Clarke belt of satellites around an exoplanet. Building on code and analysis from Korpela, Sallmen, & Leystra Greene (2015), we refine the transit analysis of Socas-Navarro (2018) by incorporating limb-darkening and taking an observer-centered approach to examining residuals. These consi...

We present all-sky maps of two major far-ultraviolet cooling lines, C iv and O vi , of highly ionized gas to investigate the nature of the transition-temperature gas. From the extinction-corrected line intensities of C iv and O vi , we calculated the gas temperature and the emission measure of the transition-temperature gas assuming isothermal plas...

Breakthrough Listen is the most comprehensive and sensitive search for extraterrestrial intelligence (SETI) to date, employing a collection of international observational facilities including both radio and optical telescopes. During the first three years of the Listen program, thousands of targets have been observed with the Green Bank Telescope (...

Advancing the scientific frontier in the search for life in the universe requires support of searches for both biosignatures and technosignatures. A modest budgetary increment can expand the search for life in the universe from primitive to complex life and from the solar neighborhood to the entire Galaxy.

Rebuttal to: ‘Deconstructing the Rio Scale: problems of subjectivity and generalization’ - Duncan Forgan, Jason Wright, Jill Tarter, Eric Korpela, Andrew Siemion, Iván Almár, Elisabeth Piotelat

The search for life in the universe is a major theme of astronomy and astrophysics for the next decade. Searches for technosignatures are complementary to searches for biosignatures, in that they offer an alternative path to discovery, and address the question of whether complex (i.e. technological) life exists elsewhere in the Galaxy. This approac...

Since 1998, Italian astrophysics institutes (now part of the Italian National Institute for Astrophysics, INAF) have been collaborating with the SETI group at the University of California, Berkeley. Thanks to this collaboration, the SERENDIP IV setup was installed at the 32-m Medicina radio telescope near Bologna, Italy. This setup was used for SET...

The Rio scale is a tool for communicating the significance of a signal to the general public. It assigns scores to signals detected in searches for extraterrestrial intelligence (SETI), which characterizes both the consequences of a signal and the probability the signal is truly from ETI, in an easily digestible format for laypeople to interpret. I...

We present the Galactic Arecibo L-Band Feed Array H i (GALFA-H i) survey data release 2 (DR2). The survey covers the 21 cm hyperfine transition of Galactic H i from -650 to 650 km ⁻¹, with 0.184 channel spacing, 4′ angular resolution, and 150 mK rms noise per 1 velocity channel. DR2 covers the entirety of the sky available from the William E. Gordo...

The Ionospheric Connection Explorer, or ICON, is a new NASA Explorer mission that will explore the boundary between Earth and space to understand the physical connection between our world and our space environment. This connection is made in the ionosphere, which has long been known to exhibit variability associated with the sun and solar wind. How...

We present the design, implementation, and on-ground performance measurements of the Ionospheric Connection Explorer EUV spectrometer, ICON EUV, a wide field (\(17^{\circ}\times 12^{\circ}\)) extreme ultraviolet (EUV) imaging spectrograph designed to observe the lower ionosphere at tangent altitudes between 100 and 500 km. The primary targets of th...

The NASA Ionospheric Connection Explorer Extreme Ultraviolet spectrograph, ICON EUV, will measure altitude profiles of the daytime extreme-ultraviolet (EUV) OII emission near 83.4 and 61.7 nm that are used to determine density profiles and state parameters of the ionosphere. This paper describes the algorithm concept and approach to inverting these...

The SETI@home project has recently completed its third year of active data analysis. Over 4 million volunteers have joined the search, providing a combined total of over 1 million CPU-years of processing power. SETI@home performs a sensitive search for extraterrestrial signals in a 2.5 MHz band centered on 1420 MHz. SETI@home searches a wide parame...

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 oxyg...

Neutral atomic hydrogen (HI) gas in interstellar space is largely organized into filaments, loops, and shells, the most prominent of which are "supershells". These gigantic structures requiring $\gtrsim 3 \times 10^{52}$ erg to form are generally thought to be produced by either the explosion of multiple supernovae (SNe) in OB associations or alter...

We employed the SERENDIP III system with the Arecibo radio telescope to search for possible artificial extraterrestrial signals. Over the four years of this search we covered 93% of the sky observable at Arecibo at least once and 44% of the sky five times or more with a sensitivity of ~3E-25 W/m2. The data were sent to a 4 million channel spectrum...

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@hom...

Galactic HI (neutral hydrogen) shells are central to our understanding of the interstellar medium (ISM), which plays a key role in the development and evolution of galaxies, including our own. Several models involving supernovae and stellar winds have contributed to our broad understanding, but a complete, detailed picture remains elusive. To exten...

We analyze potential effects of an extraterrestrial civilization's use of orbiting mirrors to illuminate the dark side of a synchronously rotating planet on planetary transit light curves. Previous efforts to detect civilizations based on side effects of planetary-scale engineering have focused on structures affecting the host star output (e.g. Dys...

The vast collecting area of the Square Kilometre Array (SKA), harnessed by sensitive receivers, flexible digital electronics and increased computational capacity, could permit the most sensitive and exhaustive search for technologically-produced radio emission from advanced extraterrestrial intelligence (SETI) ever performed. For example, SKA1-MID...

Our group is currently developing two new instruments to conduct commensal searches for extraterrestrial intelligence (SETI) at the Green Bank Telescope and Arecibo Observatory. The SETI sky surveys conducted with these two instruments will use all available receivers at these two facilities and target a range of signal types. When complete, these...

The gas in galactic disks, including our own, occurs in a wide range of temperatures and densities, most of which are unsuitable for star formation. Somehow, diffuse atomic clouds are collected into colder, denser molecular clouds that can collapse under their own gravity. The molecular condensation process is not directly observable, and the gas i...

We investigate turbulent properties of the non-star-forming, translucent molecular cloud, MBM16 by applying the statistical technique of a two-dimensional spatial power spectrum (SPS) on the neutral hydrogen (HI) observations obtained by the Galactic Arecibo L-Band Feed Array HI (GALFA-HI) survey. The SPS, calculated over the range of spatial scale...

We search for fast-expanding Hi shells associated with Galactic supernova remnants (SNRs) in the longitude range l \approx 32\arcdeg to 77\arcdeg using 21-cm line data from the Inner-Galaxy Arecibo L-band Feed Array (I-GALFA) Hi survey. Among the 39 known Galactic SNRs in this region, we find such Hi shells in four SNRs: W44, G54.4-0.3, W51C, and C...

We present a targeted search for narrow-band (<5 Hz) drifting sinusoidal radio emission from 86 stars in the Kepler field hosting confirmed or candidate exoplanets. Radio emission less than 5 Hz in spectral extent is currently known to only arise from artificial sources. The stars searched were chosen based on the properties of their putative exopl...

The interstellar medium (ISM) plays a key role in the development and evolution of galaxies, including our own. The effects of supernovae and stellar winds from generations of stars produce a turbulent, multiphase medium filled with complex interacting structures. As hot gas expands outward, it sweeps up cold neutral material into a shell. Over tim...

We are performing a transient, microsecond timescale radio sky survey, called "Astropulse," using the Arecibo telescope. Astropulse searches for brief (0.4 {\mu}s to 204.8 {\mu}s), wideband (relative to its 2.5 MHz bandwidth) radio pulses centered at 1,420 MHz. Astropulse is a commensal (piggyback) survey, and scans the sky between declinations of...

We present a catalog of 1964 isolated, compact neutral hydrogen clouds from the Galactic Arecibo L-Band Feed Array Survey Data Release One. The clouds were identified by a custom machine-vision algorithm utilizing the difference of Gaussian kernels to search for clouds smaller than 20'. The clouds have velocities typically between |V LSR| =20 and 4...

Volunteer computing, also known as public-resource computing, is a form of distributed computing that relies on members of the public donating the processing power, Internet connection, and storage capabilities of their home computers. Projects that utilize this mode of distributed computation can potentially access millions of Internet-attached ce...

The I-GALFA Survey provides a unique window on the spiral structure of the Milky Way as it contains three coherent 21 cm features that have been identified as spiral arms: the Perseus Arm, the Outer Arm, and the recently discovered Outer Scutum-Centaurus Arm. Moreover, all three of these arms lie beyond the solar circle (although the Perseus arm is...

The GALFA-HI Ultra-Compact Cloud Catalog contains over 2000 neutral hydrogen clouds associated with the Galaxy that are smaller than 20'. The properties observable at 21cm, such as position, velocity, size, and linewidth, have allowed us to separate the catalog into five populations. These include cold and warm low-velocity clouds, high-velocity c...

Interstellar gas has a variety of temperature phases, but only the coldest clouds are dense enough to collapse gravitationally and form stars. How do such clouds form? A key step in this process is the transition from neutral atomic hydrogen (HI) to molecular hydrogen (H2). To identify candidate sites where this HI-to-H2 transition may be underway,...

The Inner Galaxy ALFA (I-GALFA) survey presents a new, richly-detailed view of neutral atomic hydrogen (HI) gas in the Galactic disk. Using the Arecibo 305m radio telescope and 7-beam ALFA receiver, we have mapped all HI 21cm line emission and absorption at Galactic longitudes 32 to 77 degrees and latitudes -10 to +10 degrees, with some extensions...

We present the current status of the Berkeley SETI efforts and how they 've expanded in both the bandwidth and the time-scales over which we can detect signal. 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...

While the basic methodology of most electromagnetic searches for extraterrestrial intelligence have remained the same during the last half century, the speed and sensitivity of current searches are many orders of magnitude greater than their predecessors. Modern digital electronics and efficient algorithms allow sub-Hz spectroscopy across GHz of ba...

One of the many processes that occur in our Milky Way Galaxy is the interaction of Neutral Hydrogen (H I) shells with the Interstellar Medium (ISM). H I shells are formed when material from stellar winds and supernova explosions expands outward and mixes with the ISM. Without this phenomenon the heavy elements made in stars would not be recycled an...

To investigate the fundamental principles of H2 formation in a giant molecular cloud, we derive the H I and H2 surface density (ΣH I and ΣH2) images of the Perseus molecular cloud on sub-pc scales (~0.4 pc). We use the far-infrared data from the Improved Reprocessing of the IRAS Survey and the V-band extinction image provided by the COMPLETE Survey...

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...

We present developments in the search for engineered radio emissions from advanced extraterrestrial life. Our group is currently engaging in both targeted and sky survey searches for extraterrestrial intelligence (SETI), covering a wide variety of narrow-band and pulsed signal types. We are also developing new SETI instrumentation, designed to be f...

We present the general properties of the far-ultraviolet (FUV; 1370-1710 Å) continuum background over most of the sky, obtained with the Spectroscopy of Plasma Evolution from Astrophysical Radiation (SPEAR) instrument (also known as FIMS), flown aboard the STSAT-1 satellite mission. We find that the diffuse FUV continuum intensity is well correlate...

SETI@home, a search for signals from extraterrestrial intelligence, has been recording data at the Arecibo radio telescope since 1999. These data are sent via the Internet to the personal computers of volunteers who have donated their computers' idle time toward this search. To date, SETI@home volunteers have detected more than 4.2 billion potentia...

The distribution of a low-density transition temperature (10^4.5 - 10^5.5 K) gas in the interstellar medium conveys the character and evolution of diffuse matter in the Galaxy. This difficult to observe component of the ISM emits mainly in the far-ultraviolet (FUV) (912-1800 {\AA}) band. We describe spectral maps of FUV emission lines from the high...

Here we describe our ongoing efforts to develop high-performance and sensitive instrumentation for use in the search for extra-terrestrial intelligence (SETI). These efforts include our recently deployed Search for Extraterrestrial Emissions from Nearby Developed Intelligent Populations Spectrometer (SERENDIP V.v) and two instruments currently unde...

Here we describe our ongoing efforts to develop high-performance and sensitive instrumentation for use in the search for extra-terrestrial intelligence (SETI). These efforts include our recently deployed Search for Extraterrestrial Emissions from Nearby Developed Intelligent Populations Spectrometer (SERENDIP V.v) and two instruments currently unde...

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 using an automated 30 inch telescope. The ongoing SERENDIP V.v sky survey searches for radio signals at the 300 meter Arecibo Observatory. The currently installed confi...

The I-GALFA survey mapping all the H I in the inner Galactic disk visible to the Arecibo 305m telescope within 10 degrees of the Galactic plane (longitudes of 32 to 77 degrees at b = 0) completed observations in 2009 September and will soon be made publicly available. The high (3.4 arcmin) resolution and tremendous sensitivity of the survey offer a...

Recent high-resolution observations reveal that the HI structure of the Galaxy is quite complex with numerous filaments and clumps. Statistical techniques are essential to describe and compare these complex morphologies, which can give insights on how the energy is injected and dissipated in the interstellar medium. We use the level-crossing statis...

The GALFA-HI Survey uses 21-cm spectral line data recorded with the Arecibo L-band Feed Array (ALFA), in an effort to map the neutral hydrogen content of the Galaxy and its nearby environment. The first full public release of data (Peek et al. 2011, ApJS in press) covers approximately 7500 square degrees, from observations spanning the epoch of May...

We present the Galactic Arecibo L-Band Feed Array H I (GALFA-H I) survey and its first full data release (DR1). GALFA-H I is a high-resolution (~4'), large-area (13,000 deg2), high spectral resolution (0.18 km s-1), and wide band (–700 km s –1 < v LSR < +700 km s-1) survey of the Galactic interstellar medium in the 21 cm line hyperfine transition o...

As you have read in prior chapters, researchers have been performing progressively more sensitive SETI searches since 1960. Each search has been limited by the technologies available at the time. As radio frequency technologies have become more efficient and computers have become faster, the searches have increased in capacity and become more sensi...

Understanding the origin and nature of interstellar inhomogeneities in galaxies is a crucial step toward inclusion of realistic high-density regions in numerical simulations. Yet, driving sources and modes of interstellar turbulence -- an important ingredient for formation and evolution of interstellar structure -- have largely been unexplored even...

We present a list of candidates for previously undiscovered dwarf galaxies selected from a catalog of compact, isolated neutral hydrogen clouds identified in the GALFA-HI survey (Saul et al. 2010, in prep.). Clouds were scored based on how well their observational characteristics matched those of known Local Group dwarf galaxies, and in particular...

The contribution of future star formation fuel to a galaxy from evolved stars remains uncertain. We present a correlation of discrete clouds of HI gas with evolved variable stars and find a number of cases where stellar mass-loss is likely to have created the cloud. The results of this study impact our understanding of both stellar outflows and gal...

The conversion of atomic gas into molecular gas is a critical process for star formation. Yet, a deep understanding of fundamental agents that control the ratio of atomic to molecular gas in molecular clouds has not been achieved. Recently, Krumholz et al. (2009) provided theoretical predictions for the ratio of atomic to molecular gas in galaxies...

The faint wing-like features at velocities beyond the velocity boundaries of the Galactic rotation (Forbidden-Velocity Wings, FVWs) in the large-scale position-velocity diagrams of the HI surveys are thought to be associated with dynamical Galactic events. Most of the FVWs do not have counterparts in radio continuum or X-rays. The primary candidate...

We present a new catalog of compact, isolated neutral hydrogen clouds extracted from the first GALFA-HI data release. With 4' spatial resolution, 0.18 km/s spectral resolution, and a 80mK noise level per 1 km/s channel, the GALFA-HI survey provides a new view of neutral Galactic hydrogen. To identify isolated clouds, we developed a new algorithm ba...

We present the GALFA-H I survey. GALFA-H I is an ongoing survey of neutral hydrogen (H I) in the Galaxy conducted at the 305 m Arecibo telescope. We briefly discuss the parameters of the survey, and the philosophy behind our observational strategy. We discuss the GALFA-H I survey in the context of other large area HI surveys, past, present, and fut...

The Galactic Arecibo L-band Feed Array H I (GALFA-H I) survey is mapping the entire Arecibo sky at 21 cm, over a velocity range of –700 to +700 km s–1 (LSR), at a velocity resolution of 0.18 km s–1, and a spatial resolution of 3.5 arcmin. The unprecedented resolution and sensitivity of the GALFA-H I survey have resulted in the detection of numerous...

This paper presents first simultaneous observations of far ultraviolet (FUV) spectra of discrete and diffuse auroras, together with precipitating electrons measured on the same spacecraft, to emphasize the importance of high‐resolution FUV images for accurate estimation of precipitating energy flux in the auroral region. An FUV spectrograph image w...

The Galactic Arecibo L-band Feed Array HI (GALFA-HI) survey is mapping the entire Arecibo sky at 21-cm, over a velocity range of -700 to +700 km/s (LSR), at a velocity resolution of 0.18 km/s and an angular resolution of 3.5 arcmin. The unprecedented resolution and sensitivity of the GALFA-HI survey have resulted in the detection of many isolated,...

We discuss potential new technologies for SETI searches over the next 100 years, including new detectors for radio, infrared and optical wavelengths, improvements in computing, algorithms, and telescope arrays.

Here we describe our ongoing efforts to develop high-performance and sensitive instrumentation for use in the search for extra-terrestrial intelligence (SETI).

The I-GALFA survey is mapping all the HI in the inner Galactic disk visible to the Arecibo 305m telescope within 10 degrees of the Galactic plane (longitudes of 32 to 77 deg at b=0 deg). The survey, which will obtain 1.3 million independent spectra, became possible with the installation of the 7-beam Arecibo L-Band Feed Array (ALFA) receiver in 200...

Berkeley conducts 7 SETI programs at IR, visible and radio wavelengths. Here we review two of the newest efforts, Astropulse and Fly's Eye. A variety of possible sources of microsecond to millisecond radio pulses have been suggested in the last several decades, among them such exotic events as evaporating primordial black holes, hyper-flares from n...

Our group contributes to the Search for Extra-Terrestrial Intelligence (SETI) by developing and using world-class signal processing computers to analyze data collected on the Arecibo telescope. Although no patterned signal of extra-terrestrial origin has yet been detected, and the immediate prospects for making such a detection are highly uncertain...

We summarize radio and optical SETI programs based at the University of California, Berkeley. The ongoing SERENDIP 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 s...

The consortium for Galactic studies with the Arecibo L-band Feed Array (ALFA) is conducting a neutral hydrogen survey of the whole Arecibo sky (declination range from -1 to 38 deg), over a velocity range of -700 to +700 km/s, with high angular (3.5 arcmin) and velocity resolution (0.2 km/s). We present highlights from TOGS (Turn On GALFA Survey), t...

C IV lambdalambda1548, 1551 lines are one of the most prominent emission lines in the FUV, which are expected to detect from supernova remnants. With the SPEAR/FIMS instrument, it has already been detected and analyzed about five large angular size supernova remnants, the Vela, the Cygnus Loop, the Lupus Loop, the Monogem Ring, and the Antlia SNR....