{"id":227,"date":"2018-12-05T19:14:51","date_gmt":"2018-12-05T17:14:51","guid":{"rendered":"http:\/\/www.issibern.ch\/teams\/spacetimemetrology\/?page_id=227"},"modified":"2018-12-05T19:14:51","modified_gmt":"2018-12-05T17:14:51","slug":"recent-news","status":"publish","type":"page","link":"https:\/\/www.issibern.ch\/teams\/spacetimemetrology\/recent-news\/","title":{"rendered":"Recent News"},"content":{"rendered":"

Team members of \u201eSpacetime Metrology, Clocks and Relativistic Geodesy\u201c continued their work on the redshift corrections in application to relativistic geodesy. Recently PTB (Dr. Christian Listad<\/em> and Dr. Gesine Grosche<\/em>) made a new clock comparison between Braunschweig and Garching. Prof. Dr. J\u00fcrgen M\u00fcller <\/em>and colleagues from his group at the Institute of Geodesy at University of Hannover have shown that accurate clocks can be effectively used to unify height systems in Europe which are affected by specific offsets and tilts (see Figure 1).<\/p>\n\n\n\n
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Figure 1: Left: Simulated height system errors (offsets and tilts) up to the decimeter level in four different European regions. Right: Adjusted height errors at the centimeter level based on clock measurements; the symbols \u25a1, <\/em>\u2606<\/em>, <\/em>\u25b3<\/em>, <\/em>\u25bd<\/em> indicate the clock locations in the four regions.<\/em><\/p>\n

In a further study, they simulated clock-based measurements of the gravitational potential along a low satellite orbit and determined gravity field parameters from that kind of observation. Figure 2 shows that especially the large scale structures of the gravity field can well be recovered depending on the performance of the clocks.<\/p>\n

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\nFigure 2: Error degree variances of different gravity field solutions in terms of geoid heights with respect to the degree of a spherical harmonic expansion. The black curve gives the gravity field signal to be determined, the colored curves show the achievable accuracy for different assumptions of the clock errors ranging between 10-17<\/sup>and 10-19<\/sup> for the relative frequency observation.<\/em><\/p>\n

NIST physicist Andrew Ludlow<\/em> and colleagues achieved new atomic clock performance records in a comparison of two ytterbium optical lattice clocks at the National Institute of Standards and Technology (NIST). The clocks have achieved three new performance records, now ticking precisely enough to not only improve timekeeping and navigation, but also detect faint signals from gravity, the early universe and perhaps even dark matter https:\/\/www.nist.gov\/news-events\/news\/2018\/11\/nist-atomic-clocks-now-keep-time-well-enough-improve-models-earth<\/a><\/p>\n

Prof. Dr. Sergei Kopeikin <\/em>and colleagues from University of Missouri have significantly improved the description of the normal gravity field of relativistic ellipsoid of rotation.<\/p>\n

References:<\/u><\/strong><\/p>\n

Wu, H., M\u00fcller, J., L\u00e4mmerzahl, C.: Clock networks for height system unification: a simulation study, Geophysical Journal International, accepted Nov. 2018<\/p>\n

Mehlst\u00e4ubler, T.E., Grosche, G., Lisdat, C., Schmidt, P.O., Denker, H. (2018) Atomic clocks for geodesy. Reports on Progress in Physics Vol. 81, No. 6, 064401, https:\/\/doi.org\/10.1088\/1361-6633\/aab409<\/a><\/p>\n

Denker, H., Timmen, L., Voigt, C., Weyers, S., Peik, E., Margolis, H. S., Delva, P., Wolf, P., Petit, G. (2017) Geodetic methods to determine the relativistic redshift at the level of 10-18 in the context of international timescales \u2013 A review and practical results. Journal of Geodesy 92: 487-516. https:\/\/doi.org\/10.1007\/s00190-017-1075-1<\/a><\/p>\n

Grotti, J., Koller, S., Vogt, S., H\u00e4fner, S., Sterr, U., Lisdat, C., Denker, H., Voigt, C., Timmen, L., Rolland, A., Baynes, F.N., Margolis, H.S., Zampaolo, M., Thoumany, P., Pizzocaro, M., Rauf, B., Bregolin, F., Tampellini, A., Barbieri, P., Zucco, M., Costanzo, G.A., Clivati, C., Levi, F., Calonico, D. (2018) Geodesy and metrology with a transportable optical clock. Nature Physics 2018. https:\/\/doi.org\/10.1038\/s41567-017-0042-3<\/a><\/p>\n

Gu\u00e9na, J., Weyers, S., Abgrall, M., Grebing, C., Gerginov, V., Rosenbusch, P., Bize, S., Lipphardt, B., Denker, H., Quintin, N., Raupach, S., Nicolodi, D., Stefani, F., Chiodo, N., Koke, S., Kuhl, A., Wiotte, F., Meynadier, F., Camisard, E., Chardonnet, C., Lecoq, Y., Lours, M., Santarelli, G., Amy-Klein, A., Le Targat, R., Lopez, O., Pottie, P.-E., Grosche, G. (2017) First international comparison of fountain primary frequency standards via a long distance optical fiber link. Metrologia 54: 348\u2013354. https:\/\/doi.org\/10.1088\/1681-7575\/aa65fe<\/a><\/p>\n

McGrew, W. F., Zhang, X., Fasano, R. J., Sch\u00e4ffer, S. A., Beloy, K., Nicolodi, D., Brown, R. C., Hinkley, N., Milani, G., Schioppo, M., Yoon, T. H., Ludlow, A. D. (2018) Atomic clock performance enabling geodesy below the centimetre level. Nature (online first) https:\/\/www.nature.com\/articles\/s41586-018-0738-2<\/a><\/p>\n

Kopeikin, S.M., Vlasov, I.Y., Han W.-B. (2018) \u00a0Normal gravity field in relativistic geodesy. Physical Review D,\u00a0 Vol. 97, Issue 4, id.045020\u00a0 https:\/\/doi.org\/10.1103\/PhysRevD.97.045020<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

Team members of \u201eSpacetime Metrology, Clocks and Relativistic Geodesy\u201c continued their work on the redshift corrections in application to relativistic geodesy. Recently PTB (Dr. Christian Listad and Dr. Gesine Grosche) made a new clock comparison between Braunschweig and Garching. Prof. … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-227","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.issibern.ch\/teams\/spacetimemetrology\/wp-json\/wp\/v2\/pages\/227","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.issibern.ch\/teams\/spacetimemetrology\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.issibern.ch\/teams\/spacetimemetrology\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.issibern.ch\/teams\/spacetimemetrology\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.issibern.ch\/teams\/spacetimemetrology\/wp-json\/wp\/v2\/comments?post=227"}],"version-history":[{"count":0,"href":"https:\/\/www.issibern.ch\/teams\/spacetimemetrology\/wp-json\/wp\/v2\/pages\/227\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.issibern.ch\/teams\/spacetimemetrology\/wp-json\/wp\/v2\/media?parent=227"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}