{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T21:41:48Z","timestamp":1760218908349,"version":"build-2065373602"},"reference-count":43,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2014,2,24]],"date-time":"2014-02-24T00:00:00Z","timestamp":1393200000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/3.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Entropy"],"abstract":"<jats:p>We report on a comprehensive signal processing procedure for very low signal levels for the measurement of neutral deuterium in the local interstellar medium from a spacecraft in Earth orbit. The deuterium measurements were performed with the IBEX-Lo camera on NASA\u2019s Interstellar Boundary Explorer (IBEX) satellite. Our analysis technique for these data consists of creating a mass relation in three-dimensional time of flight space to accurately determine the position of the predicted D events, to precisely model the tail of the H events in the region where the H tail events are near the expected D events, and then to separate the H tail from the observations to extract the very faint D signal. This interstellar D signal, which is expected to be a few counts per year, is extracted from a strong terrestrial background signal, consisting of sputter products from the sensor\u2019s conversion surface. As reference we accurately measure the terrestrial D\/H ratio in these sputtered products and then discriminate this terrestrial background source. During the three years of the mission time when the deuterium signal was visible to IBEX, the observation geometry and orbit allowed for a total observation time of 115.3 days. Because of the spinning of the spacecraft and the stepping through eight energy channels the actual observing time of the interstellar wind was only 1.44 days. With the optimised data analysis we found three counts that could be attributed to interstellar deuterium. These results update our earlier work.<\/jats:p>","DOI":"10.3390\/e16021134","type":"journal-article","created":{"date-parts":[[2014,2,25]],"date-time":"2014-02-25T03:23:38Z","timestamp":1393298618000},"page":"1134-1168","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":14,"title":["Signal Processing for the Measurement of the Deuterium\/Hydrogen Ratio in the Local Interstellar Medium"],"prefix":"10.3390","volume":"16","author":[{"given":"Diego","family":"Rodr\u00edguez Moreno","sequence":"first","affiliation":[{"name":"Physics Institute, University of Bern, Sidlerstrasse 5, Bern 3012, Switzerland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2603-1169","authenticated-orcid":false,"given":"Peter","family":"Wurz","sequence":"additional","affiliation":[{"name":"Physics Institute, University of Bern, Sidlerstrasse 5, Bern 3012, Switzerland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Lukas","family":"Saul","sequence":"additional","affiliation":[{"name":"Physics Institute, University of Bern, Sidlerstrasse 5, Bern 3012, Switzerland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Maciej","family":"Bzowski","sequence":"additional","affiliation":[{"name":"Space Research Centre, Polish Academy of Sciences, Bartycka 18A, Warsaw 00-716, Poland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Marzena","family":"Kubiak","sequence":"additional","affiliation":[{"name":"Space Research Centre, Polish Academy of Sciences, Bartycka 18A, Warsaw 00-716, Poland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Justyna","family":"Sok\u00f3\u0142","sequence":"additional","affiliation":[{"name":"Space Research Centre, Polish Academy of Sciences, Bartycka 18A, Warsaw 00-716, Poland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Priscilla","family":"Frisch","sequence":"additional","affiliation":[{"name":"Department of Astronomy and Astrophysics, University of Chicago, 5640 S. Ellis Avenue, Chicago, IL 60637, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Stephen","family":"Fuselier","sequence":"additional","affiliation":[{"name":"Southwest Research Institute, San Antonio, TX 78228-0510, USA and University of Texas at San Antonio, San Antonio, TX 78249, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"David","family":"McComas","sequence":"additional","affiliation":[{"name":"Southwest Research Institute, San Antonio, TX 78228-0510, USA and University of Texas at San Antonio, San Antonio, TX 78249, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Eberhard","family":"M\u00f6bius","sequence":"additional","affiliation":[{"name":"Space Science Center and Department of Physics, University of New Hampshire, 39 College Road, Durham, NH 03824, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Nathan","family":"Schwadron","sequence":"additional","affiliation":[{"name":"Space Science Center and Department of Physics, University of New Hampshire, 39 College Road, Durham, NH 03824, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2014,2,24]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"11","DOI":"10.1007\/s11214-009-9499-4","article-title":"IBEX interstellar boundary explorer","volume":"146","author":"McComas","year":"2009","journal-title":"Sp. Sc. Rev"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"49","DOI":"10.1023\/A:1024673217736","article-title":"Atomic Deuterium\/hydrogen in the galaxy","volume":"106","author":"Linsky","year":"2003","journal-title":"Sp. Sc. Rev"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"367","DOI":"10.1007\/s11214-007-9160-z","article-title":"D\/H nearby interstellar cloud structures","volume":"130","author":"Linsky","year":"2007","journal-title":"Sp. Sc. Rev"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"003","DOI":"10.1088\/1475-7516\/2008\/09\/003","article-title":"FUSE deuterium observations: A strong case for galactic infall","volume":"9","author":"Prodanovic","year":"2008","journal-title":"J. Cosmol. Astropart. P"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"126","DOI":"10.1088\/0004-637X\/753\/2\/126","article-title":"Spitzer observations of shock-excited hydrogen deuteride in IC 443C, HH 7, and HH 54: Probing the gas-phase deuterium abundance in the dense interstellar medium","volume":"753","author":"Yuan","year":"2012","journal-title":"Astrophys. J"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1106","DOI":"10.1086\/505556","article-title":"What is the total deuterium abundance in the local galactic disk?","volume":"647","author":"Linsky","year":"2006","journal-title":"Astrophys. J"},{"key":"ref_7","first-page":"643","article-title":"Ultraviolet observations of Sirius A and Sirius B with HST-GHRS. An interstellar cloud with a possible low deuterium abundance","volume":"350","author":"Mallouris","year":"1999","journal-title":"Astron. Astrophys"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"125","DOI":"10.1051\/0004-6361\/201321420","article-title":"Evidence for direct detection of interstellar deuterium in the Local Interstellar Medium by IBEX","volume":"557","author":"Wurz","year":"2013","journal-title":"Astron. Astrophys"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"237","DOI":"10.1146\/annurev-astro-081710-102613","article-title":"The interstellar medium surrounding the sun","volume":"49","author":"Frisch","year":"2011","journal-title":"Annu. Rev. Astron. Astr"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"1291","DOI":"10.1126\/science.1221054","article-title":"The Heliosphere\u2019s interstellar interaction: No bow shock","volume":"336","author":"McComas","year":"2012","journal-title":"Science"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"53","DOI":"10.1051\/0004-6361:20078101","article-title":"The boundary conditions of the heliosphere: Photoionization models constrained by interstellar and in situ data","volume":"491","author":"Slavin","year":"2008","journal-title":"Astron. Astrophys"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"15157","DOI":"10.1029\/93JA01171","article-title":"Model of the solar wind interaction with the local interstellar medium\u2014Numerical solution of self-consistent problem","volume":"98","author":"Baranov","year":"1993","journal-title":"J. Geophys. Res"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1491","DOI":"10.1086\/505588","article-title":"Heliospheric response to different possible interstellar environments","volume":"647","author":"Frisch","year":"2006","journal-title":"Astrophys. J"},{"key":"ref_14","first-page":"103","article-title":"Change of interstellar gas parameters in stellar-wind-dominated astrospheres: Solar case","volume":"66","author":"Fahr","year":"1978","journal-title":"Astron. Astrophys"},{"key":"ref_15","first-page":"101","article-title":"Interstellar hydrogen subject to a net repulsive solar force field","volume":"77","author":"Fahr","year":"1979","journal-title":"Astron. Astrophys"},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Bonnet, R.M., Qu\u00e9merais, E., and Snow, M. (2013). Cross-Calibration of Past and Present Far UV Spectra of Solar System Objects and the Heliosphere, ISSI Scientific Report Series 13, Springer Science + Business Media. Chapter 3.","DOI":"10.1007\/978-1-4614-6384-9"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"A50","DOI":"10.1051\/0004-6361\/201321700","article-title":"Modulation of neutral interstellar He, Ne, O in the heliosphere. Survival probabilities and abundances at IBEX","volume":"557","author":"Bzowski","year":"2013","journal-title":"Astron. Astrophys"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"885","DOI":"10.1051\/0004-6361:20047147","article-title":"Coordinated observation of local interstellar helium in the heliosphere: Heliospheric conditions that affect the interstellar gas inside the heliosphere","volume":"426","author":"McMullin","year":"2004","journal-title":"Astron. Astrophys"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"73","DOI":"10.1007\/BF00170794","article-title":"Ionization processes in the heliosphere. Rates and methods of their determination","volume":"78","author":"Cummings","year":"1996","journal-title":"Sp. Sc. Rev"},{"key":"ref_20","first-page":"290","article-title":"The influence of electron impact ionization on the distribution of interstellar helium in the inner heliosphere; possible consequences for determination of interstellar helium parameters","volume":"224","author":"Fahr","year":"1989","journal-title":"Astron. Astrophys"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"14","DOI":"10.1088\/0067-0049\/198\/2\/14","article-title":"Local interstellar neutral hydrogen sampled in situ by IBEX","volume":"198","author":"Saul","year":"2012","journal-title":"Astrophys. J. Suppl. S"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"L35","DOI":"10.1051\/0004-6361:200809593","article-title":"Detectability of neutral interstellar deuterium by a forthcoming SMEX mission IBEX","volume":"483","author":"Tarnopolski","year":"2008","journal-title":"Astron. Astrophys"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"A39","DOI":"10.1051\/0004-6361\/201321166","article-title":"Assessment of detectability of neutral interstellar deuterium by IBEX observations","volume":"556","author":"Kubiak","year":"2013","journal-title":"Astron. Astrophys"},{"key":"ref_24","unstructured":"McComas, D., Allegrini, F., Bochsler, P., Bzowski, M., Collier, M., Fahr, H., Fichtner, H., Frisch, P., Funsten, H., and Fuselier, S. (, January February). The Interstellar Boundary Explorer (IBEX)."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"964","DOI":"10.1126\/science.1180927","article-title":"Structures and spectral variations of the outer heliosphere in ibex energetic neutral atom maps","volume":"326","author":"Funsten","year":"2009","journal-title":"Science"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"962","DOI":"10.1126\/science.1180981","article-title":"Width and variation of the ENA flux ribbon observed by the interstellar boundary explorer","volume":"326","author":"Fuselier","year":"2009","journal-title":"Science"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"959","DOI":"10.1126\/science.1180906","article-title":"Global observations of the interstellar interaction from the interstellar boundary explorer (IBEX)","volume":"326","author":"McComas","year":"2009","journal-title":"Science"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"966","DOI":"10.1126\/science.1180986","article-title":"Comparison of interstellar boundary explorer observations with 3D global heliospheric models","volume":"326","author":"Schwadron","year":"2009","journal-title":"Science"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"117","DOI":"10.1007\/s11214-009-9495-8","article-title":"The IBEX-Lo sensor","volume":"146","author":"Fuselier","year":"2009","journal-title":"Sp. Sc. Rev"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"75","DOI":"10.1007\/s11214-009-9504-y","article-title":"The interstellar boundary explorer high energy (IBEX-Hi) neutral atom imager","volume":"146","author":"Funsten","year":"2009","journal-title":"Sp. Sc. Rev"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"173","DOI":"10.1007\/s11214-009-9515-8","article-title":"IBEX backgrounds and signal-to-noise ratio","volume":"146","author":"Wurz","year":"2009","journal-title":"Sp. Sc. Rev"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"124502","DOI":"10.1063\/1.2821235","article-title":"The ion-optical prototype of the low energy neutral atom sensor of the Interstellar Boundary Explorer Mission (IBEX)","volume":"78","author":"Wieser","year":"2007","journal-title":"Rev. Sci. Instrum"},{"key":"ref_33","unstructured":"Scherer, K., Fichtner, H., and Marsch, E. (2000). The Outer Heliosphere: Beyond the Planets, Copernicus Gesellschafte. V."},{"key":"ref_34","unstructured":"Caballero, R., D\u2019Olivo, J.C., Medina-Tanco, G., Nellen, L., S\u00e1nchez, F.A., and Vald\u00e9s-Galicia, J.F. (, January July). Time-of-Flight Detector System with Low Background Performance for the IBEX-Lo Sensor. M\u00e9rida, Yucat\u00e1n, Mexico. Volumen 1,."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"149","DOI":"10.1007\/s11214-009-9498-5","article-title":"Diagnosingthe neutral interstellar gas flow at 1 AU with IBEX-Lo","volume":"146","author":"Kucharek","year":"2009","journal-title":"Sp. Sc. Rev"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"054904","DOI":"10.1063\/1.2842398","article-title":"Negative helium generation upon surface scattering: Application in space science","volume":"103","author":"Wurz","year":"2008","journal-title":"J. Appl. Phys"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"11","DOI":"10.1088\/0067-0049\/198\/2\/11","article-title":"Interstellar gas flow parameters derived from interstellar boundary explorer-Lo observations in 2009 and 2010: Analytical analysis","volume":"198","author":"Bochsler","year":"2012","journal-title":"Astrophys. J. Suppl. S"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"130","DOI":"10.1088\/0004-637X\/767\/2\/130","article-title":"Local interstellar hydrogen\u2019s disappearance at 1 AU: Four years of IBEX in the rising solar cycle","volume":"767","author":"Saul","year":"2013","journal-title":"Astrophys. J"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"13","DOI":"10.1088\/0067-0049\/198\/2\/13","article-title":"Estimation of the Neon\/Oxygen abundance ratio at the heliospheric termination shock and in the local interstellar medium from IBEX observations","volume":"198","author":"Bochsler","year":"2012","journal-title":"Astrophys. J. Suppl. S"},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"2092","DOI":"10.1063\/1.1139469","article-title":"Characteristics of compact solid-target charge exchange analyzers for energetic ion diagnostics on tokamaks","volume":"58","author":"Beiersdorfer","year":"1987","journal-title":"Rev. Sci. Instrum"},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"86","DOI":"10.1016\/0168-583X(93)95782-Z","article-title":"Inelastic losses of low-energy ions transmitted through thin films","volume":"78","author":"Mikheev","year":"1993","journal-title":"Nucl. Instrum. Meth. B"},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"394","DOI":"10.1380\/ejssnt.2006.394","article-title":"Particle scattering off surfaces: Application in space science","volume":"4","author":"Wurz","year":"2006","journal-title":"eJSSNT"},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"297","DOI":"10.1016\/j.pss.2011.09.009","article-title":"IBEX-Lo observations of energetic neutral hydrogen atoms originating from the lunar surface","volume":"60","author":"Rodriguez","year":"2012","journal-title":"Planet. Sp. Sci"}],"container-title":["Entropy"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1099-4300\/16\/2\/1134\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T21:08:31Z","timestamp":1760216911000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1099-4300\/16\/2\/1134"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2014,2,24]]},"references-count":43,"journal-issue":{"issue":"2","published-online":{"date-parts":[[2014,2]]}},"alternative-id":["e16021134"],"URL":"https:\/\/doi.org\/10.3390\/e16021134","relation":{},"ISSN":["1099-4300"],"issn-type":[{"type":"electronic","value":"1099-4300"}],"subject":[],"published":{"date-parts":[[2014,2,24]]}}}