Advanced technologies for satellite navigation and geodesy

Abstract

This manuscript reviews recent progress in optical frequency references and optical communication systems and discusses their utilizations in global satellite navigation systems and satellite geodesy. Lasers stabilized with optical cavities or spectroscopy of molecular iodine are analyzed, and a hybrid architecture is proposed to combine both forms of stabilization with the aim of achieving a target frequency stability of 10 -15 [s/s] over a wide range of sampling intervals.The synchronization between two optical frequency references in real-time is realized by means of time and frequency transfer on optical carriers. The technologies enabling coherent optical links are reviewed, and the development of an optical communication system for synchronization, ranging and data communication in space is described. An infrastructure exploiting the capabilities of both optical technologies for the realization of a modernized constellation of navigation satellites emitting highly synchronized signals is reviewed. Such infrastructure, named Kepler system, improves satellite navigation in terms intra-system synchronization, orbit determination accuracy, as well as system monitoring and integrity. The potential impact on geodetic key parameters is addressed.

Long-term stable optical cavity for special relativity tests in space

“…The required fractional stability and the frequency range of interest are diverse and span from values close to (in units of the square root of the power spectral density, PSD) 10 −17 Hz −1/2 at short time scales in atomic clocks [1][2][3][4][5][6] to 10 −13 Hz −1/2 at long time scales in space based laser interferometers such as the future gravitational wave detector LISA (Laser Interferometer Space Antenna) [7], the LRI (Laser Ranging Interferometer) on GRACE Follow-On (Gravity Recovery and Climate Experiment Follow-On) [8,9] and the next generation of gravity field missions [10]. Applications in future GNSS (Global Navigation Satellite Systems) concepts [11,12] will also benefit from optical cavities exhibiting stability levels in the 10 −15 Hz −1/2 range at time scales of seconds. Highstability frequency references are also key elements for tests of fundamental physics such as detection of violations of Lorentz invariance [13][14][15] through Michelson-Morley (MM) [16,17] and Kennedy-Thorndike (KT) [18,19] experiments.…”

Reference system origin and scale realization within the future GNSS constellation “Kepler”

“…Due to system-specific characteristics, e.g., the necessary estimation of epoch-wise satellite clocks, and remaining orbital model uncertainties, e.g., of the solar radiation pressure, GNSS do currently not contribute to the origin and scale realization of ITRF2014 but it might become possible in the future. A future GNSS constellation "Kepler" is proposed by the German Aerospace Center DLR featuring in addition to a Galileo-like MEO-only constellation, six LEO satellites in two polar planes as well as precise optical ISL and optical frequency references (Giorgi et al 2019b). Since the accuracy requirements of GGOS on global TRFs have not been achieved yet, it is worth investigating the impact of the proposed Kepler constellation on the origin and scale realization.…”

“…The future GNSS constellation Kepler is characterized by the innovative features of two-way optical inter-satellite links (ISL) and optical frequency references. This effort is related to the Helmholtz funded project called ADVANTAGE 2 (Advanced Technologies for Navigation and Geodesy, Giorgi et al 2019b) which is a joint effort of the German Aerospace Center DLR and the German Research Center for Geosciences GFZ. The overall project goal is to establish an architecture for a future space infrastructure for navigation and geodesy.…”

Autonomous Navigation for Mars Exploration

“…Clearly, different navigation technologies should be employed in different flight phases. The satellite navigation [8], the inertial navigation [9], the celestial navigation [10], the visual navigation [11], and the integrated navigation [12] are the most popular navigation techniques in the aerospace engineering research field. Figure 1 presents the sketch map and an example of Mars exploration.…”