The two wide-angle imaging neutral-atom spectrometers (TWINS) NASA mission-of-opportunity

D. J. McComas (Corresponding Author), F. Allegrini, J. Baldonado, B. Blake, P. C. Brandt, J. Burch, J. Clemmons, W. Crain, D. Delapp, R. DeMajistre, D. Everett, H. Fahr, L. Friesen, H. Funsten, J. Goldstein, M. Gruntman, R. Harbaugh, R. Harper, H. Henkel, C. HolmlundG. Lay, D. Mabry, D. Mitchell, U. Nass, C. Pollock, S. Pope, M. Reno, S. Ritzau, E. Roelof, E. Scime, M. Sivjee, R. Skoug, T. S. Sotirelis, M. Thomsen, C. Urdiales, P. Valek, Kai Viherkanto, S. Weidner, Tomi Ylikorpi, M. Young, J. Zoennchen

    Research output: Contribution to journalArticleScientificpeer-review

    125 Citations (Scopus)


    Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS) is a NASA Explorer Mission-of-Opportunity to stereoscopically image the Earth’s magnetosphere for the first time. TWINS extends our understanding of magnetospheric structure and processes by providing simultaneous Energetic Neutral Atom (ENA) imaging from two widely separated locations. TWINS observes ENAs from 1–100 keV with high angular (∼4°×4°) and time (∼1-minute) resolution. The TWINS Ly-α monitor measures the geocoronal hydrogen density to aid in ENA analysis while environmental sensors provide contemporaneous measurements of the local charged particle environments. By imaging ENAs with identical instruments from two widely spaced, high-altitude, high-inclination spacecraft, TWINS enables three-dimensional visualization of the large-scale structures and dynamics within the magnetosphere for the first time. This “instrument paper” documents the TWINS design, construction, calibration, and initial results. Finally, the appendix of this paper describes and documents the Southwest Research Institute (SwRI) instrument calibration facility; this facility was used for all TWINS instrument-level calibrations.
    Original languageEnglish
    Pages (from-to)157-231
    Number of pages75
    JournalSpace Science Reviews
    Issue number1-4
    Publication statusPublished - 2009
    MoE publication typeA1 Journal article-refereed


    • ENA
    • ENA instrumentation
    • Energetic neutral atom imaging
    • Geocorona
    • Magnetosphere
    • Space plasma calibration facility


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