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All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

A synoptic study of Doppler scintillation transients in the solar wind

This paper conducts the first synoptic study of Doppler scintillation transients caused by interplanetary disturbances. The Doppler scintillation data used are part of the 2.3-GHz navigation data collected by the NASA Deep Space Network when tracking planetary spacecraft during 1979-1983, a period that includes solar maximum. A total of 148 separate transients covering a heliocentric distance range of 5-179 solar radii were detected, including 26 transients detected by more than one spacecraft. The frequency of occurrence was highest near the sun and decreased with radial distance, a reflection of the radial evolution of the transients and the sensitivity of the Doppler scintillation measurements to transients. Since transients can be disruptive, as was demonstrated during the encounter of Saturn by Pioneer 11 in 1979, information on Doppler scintillation transients is essential.

Woo, Richard↗
NASA NTRS1975

Continuous observations of long-term variations in cosmic X-ray sources

Results are reported for the Charged Particle Measurements Experiment which was conducted on board IMP-7 to detect X-ray fluxes from the sun, the galactic center, Tau X-1, and Sco X-1 over a nine-month period. Autocorrelation analysis of the data indicates a probable 80-day periodicity in the flux from Sco X-1, a 110-day periodicity in the flux from the galactic center, no periodicities in the flux from Tau X-1, and a strong 27-day periodicity in the solar X-ray flux. A transient event detected within the cluster of sources constituting the galactic center is reported which lasted about two months and had a flux roughly equal to the regular flux from this area. It is noted that this was the only transient event detected in the whole area under continuous observation for the duration of the experiment.

Wende, C. D.↗
NASA NTRS2001

Quantitative Detection of Combustion Species using Ultra-Violet Diode Lasers

Southwest Sciences is developing a new microgravity combustion diagnostic based on UV diode lasers. The instrument will allow absolute concentration measurements of combustion species on a variety of microgravity combustion platforms including the Space Station. Our approach uses newly available room temperature UV diode lasers, thereby keeping the instrument compact, rugged and energy efficient. The feasibility of the technique was demonstrated by measurement of CH radicals in laboratory flames. Further progress in fabrication technology of UV diode lasers at shorter wavelengths and higher power will result in detection of transient species in the deeper UV. High sensitivity detection of combustion radicals is provided with wavelength modulation absorption spectroscopy.

Pilgrim, J. S.↗
NASA NTRS2016

Detection of Northern Hemisphere Transient Baroclinic Eddies at Gale Crater Mars

The Rover Environmental Monitoring Station (REMS) on the Mars Science Laboratory’s (MSL) Curiosity rover has been operating in Gale Crater Mars (4.5°S, 137.4°E) for over 2 Mars years. Analysis of its pressure data, which have a precision of approximately 0.2 Pa (see Haberle et al., 2014; Harri et al., 2014), reveal temporal oscillations in its seasonally de-trended daily averaged pressures at some seasons with 2-5 Pa amplitudes that have periods similar to those observed at the Viking Lander 2 (VL-2) site (48.3°N, 134.0°E) several decades ago. As illustrated in Fig 1 there are clear peaks in the variance at a frequency f approximately 0.45 and 0.06 per sol for the fall season of Mars Year (MY) 31, and at f approximately 0.15 and 0.06 per sol for MY 32. These frequencies correspond to periods of 2.2, 6.7, and 16.7 sols, and are very similar to those observed at VL-2 (Fig 2, and see Barnes, 1980). Since orbital imaging data show dust frontal systems associated with eastward traveling baroclinic eddies that occasionally cross the equator (Wang et al., 2003), these findings suggest that MSL may be seeing their signature in its pressure data. To make this case we show that (a) the spectral peaks in the MSL are not only similar to those at VL-2, they have the same seasonal variation, (b) at least for some seasons the peaks are statistically significant and not likely due to random noise in the data, and (c) Global Circulation Model (GCM) results from the Ames GCM support this interpretation.

The Rover Environmental Monitoring Station (REMS)↗
NASA NTRS2020

Detection and Mitigation of Transient Instabilities in Multi-Agent Systems and Swarms

We first introduce the novel concept of transient instabilities in multi-agent systems and swarms, i.e., a small disturbance leads to increasing-amplitude oscillations throughout the swarm, which results in a large number of inter-agent collisions. This instability is dominant in the transient phase of the system and it does not appear in the steady-state behavior of the system, as each agent uses Lyapunov-stable feedback control laws. We present a rigorous definition of transient instability in swarms, and discuss its key properties. We also present a sufficient condition to check if a swarm will be transient stable. We study the behaviour of different control laws under this condition. We also show how transient instability phenomenon could impact the dynamics of deployable structures. Next, we present a novel control architecture that augments the baseline formation maintenance controller to mitigate transient instabilities. At its heart, the proposed architecture consists of a projection operator based estimator disguised as a reference model that generates collision-free trajectories for the agents to follow. We present numerical simulation results to demonstrate the effectiveness of our proposed approaches.

Quadrelli, Marco B.↗
NASA NTRS2022

Detection and Mitigation of Transient Instabilities in Deployable Booms

Deployable space structures offer versatile uses in many space applications, as they can create very large space structures from a single space launch. However, they usually present important dynamical challenges during the critical deployment phase. In this paper, we focus on the dynamical behavior of deployable booms and the important challenge of avoiding collisions between boom’s structural elements or with other parts of the spacecraft, that can potentially have serious consequences. We define this kind of collisions as “transient instabilities” in deployable booms. A new paradigm to tackle these issues is presented in this paper, using techniques from multi-agent/swarm literature like transient instability prevention methods that avoid inter-agent collisions. We have adapted these techniques to deployable booms to guarantee safe deployment of booms and avoid collisions. We also present computational simulations of boom deployment in order to validate our techniques and demonstrate its use for future space missions.

Balas, Mark↗
NASA NTRS1987

Localization, time histories, and energy spectra of a new type of recurrent high-energy transient source

The detection of a recurrent high-energy transient source which is neither a classical X-ray nor a gamma-ray burster, but whose properties are intermediate between the two, is reported. The energy spectra of 12 recurrent events are found to be soft, characterized by kT's of 34-56 keV. The time histories are short with rise and fall times as fast as about 10 ms. The source location is a 0.12 sq deg region about 10 deg from the Galactic center.

Atteia, J.-L.↗
NASA NTRS2019

POEMMA's Target of Opportunity Sensitivity to Cosmic Neutrino Transient Sources

We calculate the sensitivity of space-based cosmic neutrino detection from transient sources in the context of the Probe Of Extreme Multi-Messenger Astrophysics (POEMMA) mission using Target- of-Opportunity (ToO) observations. POEMMA uses two spacecraft each with a large Schmidt telescope to simultaneously view the optical signals generated by extensive air showers (EASs). POEMMA is designed for both ultrahigh-energy cosmic ray and very-high-energy neutrino measurements. POEMMA has significant neutrino sensitivity starting in the 10 PeV decade via measurements of Cherenkov signals from upward-moving EASs initiated by tau neutrinos interacting in the Earth. For ToO observations, POEMMA uses the ability to quickly repoint (90° in 500 seconds) each of the two spacecraft to the direction of the transient source. POEMMA EAS measurements are performed during astronomical night, leading to different observational constraints for short- and long-duration bursts. For short-bursts of order 10(exp 3) s, POEMMA will increase the sensitivity of existing experiments (e.g., IceCube and the Pierre Auger Observatory) by up to two orders of magnitude. For long-duration bursts on the scale of 10(exp 5−6) s, the full celestial sky is available and the average neutrino sensitivity will be increased by up to a factor of 50, reaching the desired level to probe model predictions of transient neutrino sources (e.g., of blazer flares as well as both black hole-black hole and neutron star-neutron star mergers). POEMMA’s neutrino sensitivity to various models of transient neutrino sources are detailed. Altogether, our results demonstrate better sensitivity to ToO neutrino sources from the space-based POEMMA experiment compared to current ground-based experiments, and more importantly, demonstrate unique full-sky coverage for ToO neutrino sources.

Venters, Tonia M.↗
NASA NTRS2011

Semi-Supervised Novelty Detection with Adaptive Eigenbases, and Application to Radio Transients

We present a semi-supervised online method for novelty detection and evaluate its performance for radio astronomy time series data. Our approach uses adaptive eigenbases to combine 1) prior knowledge about uninteresting signals with 2) online estimation of the current data properties to enable highly sensitive and precise detection of novel signals. We apply the method to the problem of detecting fast transient radio anomalies and compare it to current alternative algorithms. Tests based on observations from the Parkes Multibeam Survey show both effective detection of interesting rare events and robustness to known false alarm anomalies.

anomaly detection↗
NASA NTRS2005

Apparatus Characterizes Transient Voltages in Real Time

The figure shows a prototype of a relatively inexpensive electronic monitoring apparatus that measures and records selected parameters of lightning-induced transient voltages on communication and power cables. The selected parameters, listed below, are those most relevant to the ability of lightning-induced transients to damage electronic equipment. This apparatus bridges a gap between some traditional transient-voltage recorders that record complete waveforms and other traditional transient-voltage recorders that record only peak values: By recording the most relevant parameters and only those parameters this apparatus yields more useful information than does a traditional peak-value (only) recorder while imposing much smaller data-storage and data-transmission burdens than does a traditional complete-waveform recorder. Also, relative to a complete-waveform recorder, this apparatus is more reliable and can be built at lower cost because it contains fewer electronic components. The transients generated by sources other than lightning tend to have frequency components well below 1 MHz. Most commercial transient recorders can detect and record such transients, but cannot respond rapidly enough for recording lightning-induced transient voltage peaks, which can rise from 10 to 90 percent of maximum amplitude in a fraction of a microsecond. Moreover, commercial transient recorders cannot rearm themselves rapidly enough to respond to the multiple transients that occur within milliseconds of each other on some lightning strikes. One transient recorder, designed for Kennedy Space Center earlier [ Fast Transient-Voltage Recorder (KSC- 11991), NASA Tech Briefs, Vol. 23, No. 10, page 6a (October 1999)], is capable of sampling transient voltages at peak values up to 50 V in four channels at a rate of 20 MHz. That recorder contains a trigger circuit that continuously compares the amplitudes of the signals on four channels to a preset triggering threshold. When a trigger signal is received, a volatile memory is filled with data for a total time of 200 ms. After the data are transferred to nonvolatile memory, the recorder rearms itself within 400 ms to enable recording of subsequent transients. Unfortunately, the recorded data must be retrieved through a serial communication link. Depending on the amount of data recorded, the memory can be filled before retrieval is completed. Although large amounts of data are recorded and retrieved, only a small part of the information (the selected parameters) is usually required. The present transient-voltage recorder provides the required information, without incurring the overhead associated with the recording, storage, and retrieval of complete transient-waveform data. In operation, this apparatus processes transient voltage waveforms in real time to extract and record the selected parameters. An analog-to-digital converter that operates at a speed of as much as 100 mega-samples per second is used to sample a transient waveform. A real-time comparator and peak detector are implemented by use of fast field-programmable gate arrays.

Medelius, Pedro↗
NASA NTRS2021

Atacama Cosmology Telescope: Detection of Millimeter-Wave Transient Sources

We report on the serendipitous discovery of three transient millimeter-wave sources using data from the Atacama Cosmology Telescope. The first, detected at R.A. = 273.8138, decl. = −49.4628 at ∼50σ total, brightened from less than 5 mJy to at least 1100 mJy at 150 GHz with an unknown rise time shorter than 13 days, during which the increase from 250 mJy to 1100 mJy took only 8 minutes. Maximum flux was observed on 2019 November 8. The source's spectral index in flux between 90–150 GHz was positive, α = 1.5 ± 0.2. The second, detected at R.A. = 105.1584, decl. = −11.2434 at ∼20σ total, brightened from less than 20 mJy to at least 300 mJy at 150 GHz with an unknown rise time shorter than 8 days. Maximum flux was observed on 2019 December 15. Its spectral index was also positive, α = 1.8 ± 0.2. The third, detected at R.A. = 301.9952, decl. = 16.1652 at ∼40σ total, brightened from less than 8 mJy to at least 300 mJy at 150 GHz over a day or less but decayed over a few days. Maximum flux was observed on 2018 September 11. Its spectrum was approximately flat, with a spectral index of α = −0.2 ± 0.1. None of the sources were polarized to the limits of these measurements. The two rising-spectrum sources are coincident in position with M and K stars, while the third is coincident with a G star.

Time domain astronomy↗
NASA NTRS1983

Coronal transients in FE XIV 5303A: First two-dimensional photoelectric ground-based observations

An observational program was undertaken at Sacramento Peak Observatory to photoelectrically detect coronal transients. Continuous observations are made in the Fe XIV 5303A green line, utilizing the 40 cm coronagraph and the Photoelectric Coronal Photometer. Scans at three heights above the limb are combined to form a low resolution picture of the greenline corona every 20 to 30 minutes. Difference pictures, relative to an initial scan, are generated to search for sudden changes in the corona. The first few days of operation of this program have yielded three low-lying events ( 1.55 solar radii) following minor chromospheric activity (a surge and eruptive prominences), which propagated up through the corona with velocities on the order of 100 km/s.

Altrock, R. C.↗
NASA NTRS1989

Transient fault behavior in a microprocessor: A case study

An experimental analysis is described which studies the susceptibility of a microprocessor based jet engine controller to upsets caused by current and voltage transients. A design automation environment which allows the run time injection of transients and the tracing from their impact device to the pin level is described. The resulting error data are categorized by the charge levels of the injected transients by location and by their potential to cause logic upsets, latched errors, and pin errors. The results show a 3 picoCouloumb threshold, below which the transients have little impact. An Arithmetic and Logic Unit transient is most likely to result in logic upsets and pin errors (i.e., impact the external environment). The transients in the countdown unit are potentially serious since they can result in latched errors, thus causing latent faults. Suggestions to protect the processor against these errors, by incorporating internal error detection and transient suppression techniques, are also made.

Duba, Patrick↗
NASA NTRS1992

Characteristics of CMEs observed in the heliosphere using Helios photometer data

The zodiacal light photometers on the two Helios spacecraft have been used to detect and study mass ejections and other phenomena emanating from the sun and traversing the heliosphere within 1 AU. We have recently compiled a complete list of all of the significant white light transient events detected from the 90-deg photometers on both Helios spacecraft. This is a preliminary report on the long-term frequency of occurrence of these events; it emphasizes newly processed data from Helios-l from 1975 through 1982 and viewed south of the ecliptic. With the large Helios photometer data base, we will be able to identify the fraction of the 90 deg events which are heliospheric CMEs and determine their characteristics.

Webb, D. F.↗
NASA NTRS2019

Radio Follow-up of a Candidate γ-Ray Transient in the Sky Localization Area of GW170608

After the identification of a candidate γ-ray transient in the error region of the binary black hole (BBH) merger GW150914 by the Fermi satellite, the question of whether BBH mergers can be associated with electromagnetic counterparts remains highly debated. Here, we present radio follow-up observations of GW170608, a BBH merger that occurred during the second observing run (O2) of the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO). Our radio follow-up focused on a specific field contained in the GW170608 sky localization area, where a candidate high-energy transient was detected by the Fermi Large Area Telescope (LAT). We make use of data collected at 1.4 GHz with the Karl G. Jansky Very Large Array (VLA), as well as with the VLA Lowband Ionosphere and Transient Experiment (VLITE). Our analysis is sensitive to potential radio afterglows with luminosity densities L(1.4GHz) ≳ 6 x 10^(28) erg/sHz. In the most optimistic theoretical models, ≈20% of BBH events occurring in massive hosts could be associated with outflows as radio luminous as this. Although we find no evidence for the presence of a radio counterpart associated with the LAT candidate in the GW170608 error region, our analysis demonstrates the feasibility of future radio follow-up observations of well-localized BBHs. Comparing our radio upper limits with theoretical expectations for the radio afterglows potentially associated with jets launched in BBH mergers, we find that for jets of energy ≈10^(49) erg seen on-axis, only jet angles θ(jet)≳40° are compatible with the observations.

Kyle Artkop↗