The Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS) NASA Mission-of-Opportunity

McComas, D. J.; Allegrini, F.; Baldonado, J. R.; Blake, B.; Brandt, P. C.; Burch, J. L.; Clemmons, J. H.; Crain, William R.; Delapp, D.; Demajistre, R.; Everett, D.; Fahr, H. J.; Friesen, L. M.; Funsten, H. O.; Goldstein, J.; Gruntman, M.; Harbaugh, R.; Harper, R. W.; Henkel, H.; Holmlund, Christer; Lay, G.; Mabry, D. J.; Mitchell, D. G.; Nass, U.; Pollock, C. J.; Pope, S.; Reno, M.; Ritzau, S. M.; Roelof, E. C.; Scime, Earl; Sivjee, Mazaher G.; Skoug, R. M.; Sotirelis, T.; Thomsen, M. F.; Urdiales, C.; Valek, P. W.; Viherkanto, Kai; Weidner, S.; Ylikorpi, Tomi; Young, Michael K.; Zoennchen, Jochen

doi:10.1007/s11214-008-9467-4

Cited by 131 publications

(169 citation statements)

References 70 publications

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“…A detailed description of this facility can be found in Ref. 25. The ion beams are monitored by a MCPbased 2D imaging counter to confirm uniformity throughout the injection window for CoDICE-Hi and -Lo.…”

Section: A Calibration Facilitiesmentioning

confidence: 99%

An integrated time-of-flight versus residual energy subsystem for a compact dual ion composition experiment for space plasmas

Desai

Ogasawara

Ebert

et al. 2015

Review of Scientific Instruments

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We have developed a novel concept for a Compact Dual Ion Composition Experiment (CoDICE) that simultaneously provides high quality plasma and energetic ion composition measurements over 6 decades in ion energy in a wide variety of space plasma environments. CoDICE measures the two critical ion populations in space plasmas: (1) mass and ionic charge state composition and 3D velocity and angular distributions of ∼10 eV/q–40 keV/q plasma ions—CoDICE-Lo and (2) mass composition, energy spectra, and angular distributions of ∼30 keV–10 MeV energetic ions—CoDICE-Hi. CoDICE uses a common, integrated Time-of-Flight (TOF) versus residual energy (E) subsystem for measuring the two distinct ion populations. This paper describes the CoDICE design concept, and presents results of the laboratory tests of the TOF portion of the TOF vs. E subsystem, focusing specifically on (1) investigation of spill-over and contamination rates on the start and stop microchannel plate (MCP) anodes vs. secondary electron steering and focusing voltages, scanned around their corresponding model-optimized values, (2) TOF measurements and resolution and angular resolution, and (3) cross-contamination of the start and stop MCPs’ singles rates from CoDICE-Lo and -Hi, and (4) energy resolution of avalanche photodiodes near the lower end of the CoDICE-Lo energy range. We also discuss physical effects that could impact the performance of the TOF vs. E subsystem in a flight instrument. Finally, we discuss advantages of the CoDICE design concept by comparing with capabilities and resources of existing flight instruments.

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Section: A Calibration Facilitiesmentioning

confidence: 99%

An integrated time-of-flight versus residual energy subsystem for a compact dual ion composition experiment for space plasmas

Desai

Ogasawara

Ebert

et al. 2015

Review of Scientific Instruments

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“…[8] A full description of the TWINS mission of opportunity is given in McComas et al [2009a]. The two spacecraft are in Molniya orbits with inclinations of 63.4 , perigee altitudes of $1000 km, and apogees in the northern hemisphere at $7.2 R E .…”

Section: Twins Instrumentationmentioning

confidence: 99%

“…[3] Valek et al [2010] reported observations of energetic neutral atom (ENA) images from the TWINS mission [McComas et al, 2009a] for a storm on 22 July 2009 that we will classify in this study as a CIR storm. The fact that the TWINS mission has two satellites provides nearly continuous coverage of the storm over a period of 8 h, TWINS1 during the main phase and TWINS2 during the early recovery phase, in which equatorial ion intensities can be extracted from the TWINS ENA images.…”

Section: Introductionmentioning

confidence: 99%

Evolution of CIR storm on 22 July 2009

et al. 2012

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[1] Global images of ion intensities are deconvolved from TWINS ENA images during the main and recovery phase of a CIR storm on 22 July 2009. The global spatial ion images taken at different times, along with solar wind data, geomagnetic activity indices, geosynchronous orbit observations, and in situ measurements from the THEMIS mission provide a picture of the evolution of the ring current during both the main phase and early recovery phase of the storm. Major features of the evolution are consistent with expectations based upon time dependent geomagnetic indices, e.g., SYM/H and ASY/H, and geosynchronous orbit detection of dipolarizations from GOES 11 and 12. Direct comparisons are made with in situ THEMIS ESA and SST spectral measurements. The peak energy of the ion spectrum in the ring current is seen to decrease in the recovery phase. The time evolution of the ion energy spectra over the range from 2.5 to 97.5 keV at the spatial peaks of the ring current in the inner magnetosphere obtained from ENA images is presented for the first time.

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“…Onboard the two TWINS (Two Wide-angle Imaging Neutral-atom Spectrometers) satellites (McComas et al, 2009). The Lyman-α detectors (LADs) have provided nearly continuous, circumterrestrial Lyman-α monitoring of the exosphere (from geocentric distances between ≈ 4.5 and 7.2 R e ) since 2008.…”

Section: Introductionmentioning

confidence: 99%

The response of the H geocorona between 3 and 8 Re to geomagnetic disturbances studied using TWINS stereo Lyman-α data

Zoennchen¹,

Nass²,

Fahr³

et al. 2017

Ann. Geophys.

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Abstract. Circumterrestrial Lyman-α column brightness observations from 3-8 Earth radii (R e ) have been used to study temporal density variations in the exospheric neutral hydrogen as response to geomagnetic disturbances of different strength, i.e., Dst peak values between −26 and −147 nT. The data used were measured by the two Lyman-α detectors (LAD1/2) onboard both TWINS satellites between the solar minimum of 2008 and near the solar maximum of 2013. The solar Lyman-α flux at 121.6 nm is resonantly scattered near line center by exospheric H atoms and measured by the TWINS LADs. Along a line of sight (LOS), the scattered LOS-column intensity is proportional to the LOS H column density, assuming optically thin conditions above 3 R e . In the case of the eight analyzed geomagnetic storms we found a significant increase in the exospheric Lyman-α flux between 9 and 23 % (equal to the same increase in H column density n H ) compared to the undisturbed case short before the storm event. Even weak geomagnetic storms (e.g., Dst peak values ≥ −41 nT) under solar minimum conditions show increases up to 23 % of the exospheric H densities. The strong H density increase in the observed outer exosphere is also a sign of an enhanced H escape flux during storms. For the majority of the storms we found an average time shift of about 11 h between the time when the first significant dynamic solar wind pressure peak (p SW ) hits the Earth and the time when the exospheric Lyman-α flux variation reaches its maximum. The results show that the (relative) exospheric density reaction of n H have a tendency to decrease with increasing peak values of Dst index or the Kp index daily sum. Nevertheless, a simple linear correlation between n H and these two geomagnetic indices does not seem to exist. In contrast, when recovering from the peak back to the undisturbed case, the Kp index daily sum and the n H essentially show the same temporal recovery.Keywords. Atmospheric composition and structure (airglow and aurora; pressure density and temperature) -meteorology and atmospheric dynamics (thermospheric dynamics)

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The Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS) NASA Mission-of-Opportunity

Cited by 131 publications

References 70 publications

An integrated time-of-flight versus residual energy subsystem for a compact dual ion composition experiment for space plasmas

An integrated time-of-flight versus residual energy subsystem for a compact dual ion composition experiment for space plasmas

Evolution of CIR storm on 22 July 2009

The response of the H geocorona between 3 and 8 <i>R</i><sub>e</sub> to geomagnetic disturbances studied using TWINS stereo Lyman-<i>α</i> data

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The Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS) NASA Mission-of-Opportunity

Cited by 131 publications

References 70 publications

An integrated time-of-flight versus residual energy subsystem for a compact dual ion composition experiment for space plasmas

An integrated time-of-flight versus residual energy subsystem for a compact dual ion composition experiment for space plasmas

Evolution of CIR storm on 22 July 2009

The response of the H geocorona between 3 and 8 &lt;i&gt;R&lt;/i&gt;&lt;sub&gt;e&lt;/sub&gt; to geomagnetic disturbances studied using TWINS stereo Lyman-&lt;i&gt;α&lt;/i&gt; data

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The response of the H geocorona between 3 and 8 <i>R</i><sub>e</sub> to geomagnetic disturbances studied using TWINS stereo Lyman-<i>α</i> data