{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,16]],"date-time":"2026-04-16T04:11:12Z","timestamp":1776312672671,"version":"3.50.1"},"reference-count":32,"publisher":"MDPI AG","issue":"16","license":[{"start":{"date-parts":[[2022,8,21]],"date-time":"2022-08-21T00:00:00Z","timestamp":1661040000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100000844","name":"European Space Agency (ESA)","doi-asserted-by":"publisher","award":["4000134527\/21\/NL\/AD"],"award-info":[{"award-number":["4000134527\/21\/NL\/AD"]}],"id":[{"id":"10.13039\/501100000844","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100000844","name":"European Space Agency (ESA)","doi-asserted-by":"publisher","award":["SFB 1464"],"award-info":[{"award-number":["SFB 1464"]}],"id":[{"id":"10.13039\/501100000844","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100000844","name":"European Space Agency (ESA)","doi-asserted-by":"publisher","award":["EXC-2123"],"award-info":[{"award-number":["EXC-2123"]}],"id":[{"id":"10.13039\/501100000844","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Deutsche Forschungsgemeinschaft","award":["4000134527\/21\/NL\/AD"],"award-info":[{"award-number":["4000134527\/21\/NL\/AD"]}]},{"name":"Deutsche Forschungsgemeinschaft","award":["SFB 1464"],"award-info":[{"award-number":["SFB 1464"]}]},{"name":"Deutsche Forschungsgemeinschaft","award":["EXC-2123"],"award-info":[{"award-number":["EXC-2123"]}]},{"name":"Clusters of Excellence","award":["4000134527\/21\/NL\/AD"],"award-info":[{"award-number":["4000134527\/21\/NL\/AD"]}]},{"name":"Clusters of Excellence","award":["SFB 1464"],"award-info":[{"award-number":["SFB 1464"]}]},{"name":"Clusters of Excellence","award":["EXC-2123"],"award-info":[{"award-number":["EXC-2123"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>The precise tracking of distance variations between two satellites in low Earth orbit can provide key data for the understanding of the Earth\u2019s system, specifically on seasonal and sub-seasonal water cycles and their impact on water levels. Measured distance variations, caused by local variations in gravitational field, serve as inputs to complex gravity models with which the movement of water on the globe can be identified. Satellite missions GOCE (2009\u20132013) and GRACE (2002\u20132017) delivered a significant improvement to our understanding of spatial and temporal gravity variations. Since 2018, GRACE Follow-On has been providing data continuity and features for the first time through the use of a laser interferometer as the technology demonstrator, in addition to a microwave ranging system as the main instrument. The laser interferometer provides an orders-of-magnitude lower measurement noise, and thereby could enable a significant improvement in the measurement of geoids if combined with suitable improvements in auxiliary instrumentation and Earth system modelling. In order to exploit the improved ranging performance, the ESA is investigating the design of a \u2018Next Generation Gravity Mission\u2019, consisting of two pairs of satellites with laser interferometers, improved accelerometers and improved platform performance. In this paper, we present the current design of the laser interferometer developed by us, the development status of the individual instrument units and the options available.<\/jats:p>","DOI":"10.3390\/rs14164089","type":"journal-article","created":{"date-parts":[[2022,8,22]],"date-time":"2022-08-22T01:56:40Z","timestamp":1661133400000},"page":"4089","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":11,"title":["Towards NGGM: Laser Tracking Instrument for the Next Generation of Gravity Missions"],"prefix":"10.3390","volume":"14","author":[{"given":"Kolja","family":"Nicklaus","sequence":"first","affiliation":[{"name":"Spacetech GmbH, Seelbachstr. 13, D-88090 Immenstaad, Germany"}]},{"given":"Kai","family":"Voss","sequence":"additional","affiliation":[{"name":"Spacetech GmbH, Seelbachstr. 13, D-88090 Immenstaad, Germany"}]},{"given":"Anne","family":"Feiri","sequence":"additional","affiliation":[{"name":"Spacetech GmbH, Seelbachstr. 13, D-88090 Immenstaad, Germany"}]},{"given":"Marina","family":"Kaufer","sequence":"additional","affiliation":[{"name":"Spacetech GmbH, Seelbachstr. 13, D-88090 Immenstaad, Germany"}]},{"given":"Christian","family":"Dahl","sequence":"additional","affiliation":[{"name":"Spacetech GmbH, Seelbachstr. 13, D-88090 Immenstaad, Germany"}]},{"given":"Mark","family":"Herding","sequence":"additional","affiliation":[{"name":"Spacetech GmbH, Seelbachstr. 13, D-88090 Immenstaad, Germany"}]},{"given":"Bailey Allen","family":"Curzadd","sequence":"additional","affiliation":[{"name":"Spacetech GmbH, Seelbachstr. 13, D-88090 Immenstaad, Germany"}]},{"given":"Andreas","family":"Baatzsch","sequence":"additional","affiliation":[{"name":"Spacetech GmbH, Seelbachstr. 13, D-88090 Immenstaad, Germany"}]},{"given":"Johanna","family":"Flock","sequence":"additional","affiliation":[{"name":"Spacetech GmbH, Seelbachstr. 13, D-88090 Immenstaad, Germany"}]},{"given":"Markus","family":"Weller","sequence":"additional","affiliation":[{"name":"Spacetech GmbH, Seelbachstr. 13, D-88090 Immenstaad, Germany"}]},{"given":"Vitali","family":"M\u00fcller","sequence":"additional","affiliation":[{"name":"Max-Planck-Institut f\u00fcr Gravitationsphysik (Albert-Einstein-Institut), Callinstrasse 38, D-30167 Hannover, Germany"},{"name":"Institut f\u00fcr Gravitationsphysik, Leibniz Universit\u00e4t Hannover, Callinstrasse 38, D-30167 Hannover, Germany"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1661-7868","authenticated-orcid":false,"given":"Gerhard","family":"Heinzel","sequence":"additional","affiliation":[{"name":"Max-Planck-Institut f\u00fcr Gravitationsphysik (Albert-Einstein-Institut), Callinstrasse 38, D-30167 Hannover, Germany"},{"name":"Institut f\u00fcr Gravitationsphysik, Leibniz Universit\u00e4t Hannover, Callinstrasse 38, D-30167 Hannover, Germany"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7657-8840","authenticated-orcid":false,"given":"Malte","family":"Misfeldt","sequence":"additional","affiliation":[{"name":"Max-Planck-Institut f\u00fcr Gravitationsphysik (Albert-Einstein-Institut), Callinstrasse 38, D-30167 Hannover, Germany"},{"name":"Institut f\u00fcr Gravitationsphysik, Leibniz Universit\u00e4t Hannover, Callinstrasse 38, D-30167 Hannover, Germany"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7613-3681","authenticated-orcid":false,"given":"Juan Jose Esteban","family":"Delgado","sequence":"additional","affiliation":[{"name":"Max-Planck-Institut f\u00fcr Gravitationsphysik (Albert-Einstein-Institut), Callinstrasse 38, D-30167 Hannover, Germany"},{"name":"Institut f\u00fcr Gravitationsphysik, Leibniz Universit\u00e4t Hannover, Callinstrasse 38, D-30167 Hannover, Germany"}]}],"member":"1968","published-online":{"date-parts":[[2022,8,21]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"819","DOI":"10.1007\/s00190-011-0467-x","article-title":"First GOCE gravity field models derived by three different approaches","volume":"85","author":"Pail","year":"2011","journal-title":"J. Geod."},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Dahle, C., Murb\u00f6ck, M., Flechtner, F., Dobslaw, H., Michalak, G., Neumayer, K.H., Abrykosov, O., Reinhold, A., K\u00f6nig, R., and Sulzbach, R. (2019). The GFZ GRACE RL06 monthly gravity field time series: Processing details and quality assessment. Remote Sens., 11.","DOI":"10.3390\/rs11182116"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"e2020GL088306","DOI":"10.1029\/2020GL088306","article-title":"Extending the global mass change data record: GRACE Follow-On instrument and science data performance","volume":"47","author":"Landerer","year":"2020","journal-title":"Geophys. Res. Lett."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"e2019GL086926","DOI":"10.1029\/2020GL087291","article-title":"Continuity of the mass loss of the world\u2019s glaciers and ice caps from the GRACE and GRACE Follow-On missions","volume":"47","author":"Velicogna","year":"2020","journal-title":"Geophys. Res. Lett."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"e2020GL090656","DOI":"10.1029\/2020GL090656","article-title":"Global ocean mass change from GRACE and GRACE Follow-On and altimeter and Argo measurements","volume":"47","author":"Chen","year":"2020","journal-title":"Geophys. Res. Lett."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"733","DOI":"10.1002\/2015JD023808","article-title":"Does GRACE see the terrestrial water cycle \u201cintensifying\u201d?","volume":"121","author":"Eicker","year":"2016","journal-title":"J. Geophys. Res. Atmos."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"931","DOI":"10.2514\/1.A34326","article-title":"GRACE-FO: The Gravity Recovery and Climate Experiment Follow-On Mission","volume":"56","author":"Kornfeld","year":"2019","journal-title":"J. Spacecr. Rocket."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"1083","DOI":"10.1007\/s00190-012-0566-3","article-title":"Intersatellite laser ranging instrument for the GRACE follow-on mission","volume":"86","author":"Sheard","year":"2012","journal-title":"J. Geod."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"031101","DOI":"10.1103\/PhysRevLett.123.031101","article-title":"In-Orbit Performance of the GRACE Follow-On Laser Ranging Interferometer","volume":"123","author":"Abich","year":"2019","journal-title":"Phys. Rev. Lett."},{"key":"ref_10","unstructured":"Bender, P.L., Wiese, D., and Nerem, R.S. (2008, January 23\u201325). A Possible dual-grace mission with 90 degree and 63 degree inclination orbits. Proceedings of the 3rd International Symposium on Formation Flying, Missions and Technologies, ESA\/ESTEC, Noordwijk, The Netherlands. Available online: https:\/\/www.worldcat.org\/title\/proceedings-of-the-3rd-international-symposium-on-formation-flying-missions-and-technologies-23-25-april-2008-esa-estec-noordwijk-the-netherlands\/oclc\/809927086?referer=di&ht=edition."},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Pail, R., Yeh, H.-C., Feng, W., Hauk, M., Purkhauser, A., Wang, C., Zhong, M., Shen, Y., Chen, Q., and Luo, Z. (2019). Next-Generation Gravity Missions: Sino-European Numerical Simulation Comparison Exercise. Remote Sens., 11.","DOI":"10.3390\/rs11222654"},{"key":"ref_12","unstructured":"Gruber, T., Panet, I., and E.motion2 Team (2022, July 27). Proposal to ESA\u2019s Earth Explorer Call 9: Earth System Mass Transport Mission-E.motion2. Deutsche Geod\u00e4tische Kommission der Bayerischen Akademie der Wissenschaften, Reihe B, Angewandte Geod\u00e4sie, Series B, Available online: https:\/\/dgk.badw.de\/fleadmin\/user_upload\/Files\/DGK\/docs\/b-318.pdf."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"e2021JB022392","DOI":"10.1029\/2021JB022392","article-title":"Time Variable Earth Gravity Field Models from the First Spaceborne Laser Ranging Interferometer","volume":"126","author":"Pie","year":"2021","journal-title":"J. Geophys. Res. Solid Earth"},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Flechtner, F., Neumayer, K.H., Dahle, C., Dobslaw, H., Fagiolini, E., Raimondo, J.C., and G\u00fcntner, A. (2016). What can be expected from the GRACE-FO laser ranging interferometer for earth science applications?. Remote Sensing and Water Resources, Springer International Publishing.","DOI":"10.1007\/978-3-319-32449-4_11"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"e2020GL089445","DOI":"10.1029\/2020GL089445","article-title":"GRACE Follow-On laser ranging interferometer measurements uniquely distinguish short-wavelength gravitational perturbations","volume":"47","author":"Han","year":"2020","journal-title":"Geophys. Res. Lett."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"e2021JB022983","DOI":"10.1029\/2021JB022983","article-title":"Along-orbit analysis of GRACE Follow-On inter-satellite laser ranging measurements for sub-monthly surface mass variations","volume":"127","author":"Han","year":"2022","journal-title":"J. Geophys. Res. Solid Earth"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"e2021GL095157","DOI":"10.1029\/2021GL095157","article-title":"Spatiotemporal Characterization of Geophysical Signal Detection Capabilities of GRACE-FO","volume":"49","author":"Peidou","year":"2022","journal-title":"Geophys. Res. Lett."},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Behzadpour, S., Kvas, A., and Mayer-G\u00fcrr, T. (2021, January 19\u201330). GRACE Follow-On Gravity Field Recovery from Combined Laser Ranging Interferometer and Microwave Ranging System Measurements. Proceedings of the EGU General Assembly Conference Abstracts, Online.","DOI":"10.5194\/egusphere-egu21-9415"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"313","DOI":"10.1007\/s12567-020-00324-6","article-title":"Laser metrology concept consolidation for NGGM","volume":"12","author":"Nicklaus","year":"2020","journal-title":"CEAS Space J."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"1362","DOI":"10.2514\/1.A34790","article-title":"Tilt-to-Length Coupling in the GRACE Follow-On Laser Ranging Interferometer","volume":"57","author":"Wegener","year":"2020","journal-title":"J. Spacecr. Rocket."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"19209","DOI":"10.1109\/JSEN.2021.3090790","article-title":"Analysis of GRACE Follow-On Laser Ranging Interferometer derived inter-satellite pointing angles","volume":"21","author":"Goswami","year":"2021","journal-title":"IEEE Sens. J."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"054013","DOI":"10.1103\/PhysRevApplied.14.054013","article-title":"Tracking-Length and Differential-Wave-Front-Sensing Signals from Quadrant Photodiodes in Heterodyne Interferometers with Digital Phase-Locked Loop Readout","volume":"14","author":"Heinzel","year":"2020","journal-title":"Phys. Rev. Appl."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"26014","DOI":"10.1364\/OE.434483","article-title":"Absolute frequency readout derived from ULE cavity for next generation geodesy missions","volume":"29","author":"Rees","year":"2021","journal-title":"Opt. Express"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"11351","DOI":"10.1364\/OE.22.011351","article-title":"Laser link acquisition demonstration for the GRACE Follow-On mission","volume":"22","author":"Wuchenich","year":"2014","journal-title":"Opt. Express"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"5251","DOI":"10.1364\/OL.39.005251","article-title":"Weak-light phase tracking with a low cycle slip rate","volume":"39","author":"Francis","year":"2014","journal-title":"Opt. Lett."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"1075","DOI":"10.1142\/S021827180200258X","article-title":"Pico-Watt and Femto-Watt Weak-Light Phase Locking","volume":"11","author":"Liao","year":"2002","journal-title":"Int. J. Mod. Phys. D"},{"key":"ref_27","unstructured":"(2022, July 27). LISA Mission L3 Proposal. Available online: https:\/\/www.elisascience.org\/files\/publications\/LISA_L3_20170120.pdf."},{"key":"ref_28","unstructured":"Barke, S., Brause, N., Bykov, I., Delgado, J.J.E., Enggaard, A., Gerberding, O., Heinzel, G., Kullmann, J., Perdersen, S.M., and Rasmussen, T. (2022, July 27). LISA Metrology System. Available online: https:\/\/pure.mpg.de\/rest\/items\/item_2058697_2\/component\/file_2058696\/content."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"074501","DOI":"10.1063\/1.4927071","article-title":"Readout for intersatellite laser interferometry: Measuring low frequency phase fluctuations of high-frequency signals with microradian precision","volume":"86","author":"Gerberding","year":"2015","journal-title":"Rev. Sci. Instrum."},{"key":"ref_30","first-page":"1","article-title":"Optical phase readout instrument for picometer-level precision heterodyne interferometers","volume":"247","author":"Delgado","year":"2022","journal-title":"Sens. Transducers J."},{"key":"ref_31","unstructured":"McNamara, P., and Racca, G. (2022, July 27). Introduction to LISA pathfinder, LISA-LPF-RP-0002, 30 March 2009. Available online: https:\/\/sci.esa.int\/documents\/34614\/36035\/1567257332401-LISA-LPFRP-0002.pdf."},{"key":"ref_32","unstructured":"Delgado, E., and Jos\u00e9, J. (2012). Laser Ranging and Data Communication for the Laser Interferometer Space Antenna. [Ph.D. Thesis, Universidad de Granada]. Available online: https:\/\/digibug.ugr.es\/handle\/10481\/21038."}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/14\/16\/4089\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T00:13:09Z","timestamp":1760141589000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/14\/16\/4089"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2022,8,21]]},"references-count":32,"journal-issue":{"issue":"16","published-online":{"date-parts":[[2022,8]]}},"alternative-id":["rs14164089"],"URL":"https:\/\/doi.org\/10.3390\/rs14164089","relation":{},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2022,8,21]]}}}