Time Transfer From GPS for Designing a SmallSat-Based Lunar Navigation Satellite System

Abstract

With the advent of new frontiers in space exploration, traveling to the Moon serves as a crucial stepping stone for the success of future deep space missions. Many international space agencies, such as the National Aeronautics and Space Administration (NASA), European Space Agency (ESA), China National Space Administration (CNSA), Japan Aerospace Exploration Agency (JAXA), and Roscosmos State Corporation for Space Activities (Roscosmos), have demonstrated a growing interest in building a sustainable human presence on the Moon (Laurini & Gerstenmaier, 2014). More than 40 lunar missions are being planned within the next decade by 10 international space agencies (Tai et al., 2020). After more than 50 years since the Apollo program ended, NASA's Artemis mission will land humans on the Moon in the mid-2020s, including the first woman and first person of color (Smith et al., 2020). Furthermore, active efforts on traveling to the Moon are also being invested in by private sector companies like SpaceX and Blue Origin.User position, navigation, and timing (PNT) serves as the basis for various lunar applications that include mission activity planning, search-and-rescue operations, and geotagging calibrated scientific payload data samples (Israel et al., 2020).

A Case Study Analysis for Designing a Lunar Navigation Satellite System with Time Transfer from the Earth GPS

“…This value is essentially one order of magnitude higher than that of the Earth GPS and aligns with the desired position requirements of lunar navigation satellites listed in National Aeronautics and Space Administration, 2022, i.e., < 4 m, 1-σ RSS. Our prior work provides a sensitivity analysis (Bhamidipati, Mina, & Gao, 2022a), wherein the timing errors and lunar UERE values are analyzed as the ephemeris errors vary at 0.3 m, 3 m, 30 m, and 300 m. The timing filter's time update step is executed every T pred s. = 60 Details regarding the reduced update rate with a sampling period of T mT meas pred = for the measurement update will be discussed below.…”

“…In our prior work (Bhamidipati et al, 2021(Bhamidipati et al, , 2022a, we designed an LNSS architecture that harnessed the legacy Earth GPS to provide precise timing corrections to the onboard clock, as depicted in Figure 1. The time-transfer technique leverages intermittently available Earth-GPS signals to alleviate the SWaP requirements of the onboard clocks and to mitigate the need for an extensive ground monitoring infrastructure on the Moon.…”

“…Given that many design choices, including the grade of the onboard clock and the orbit type, still need to be finalized for the future SmallSat-based LNSS, in this study, we extend upon prior work (Bhamidipati et al, 2021(Bhamidipati et al, , 2022a to analyze the LNSS performance using the proposed time-transfer architecture (in Figure 1) from the Earth GPS under various case studies. Specifically, an LNSS satellite is simulated in various lunar orbit types, including an ELFO, LLO, PCO, and NRHO, and equipped with different grades of onboard clocks.…”

Precise Positioning and Timekeeping in a Lunar Orbit via Terrestrial GPS Time-Differenced Carrier-Phase Measurements

“…Capuano et al (2016) and Capuano et al (2017) developed an orbital filter that fuses observations of terrestrial GPS pseudorange and pseudorange rate with an orbital force model through an adaptive extended Kalman filter framework. In our prior works (Bhamidipati et al, 2022a(Bhamidipati et al, , 2022b, we successfully demonstrated the use of terrestrial GPS pseudoranges to achieve precise and standalone timing onboard small satellites (SmallSats) in various lunar orbits such as low lunar orbit, prograde circular orbit, ELFO, and NRHO. In another prior work (Iiyama et al, 2021), we developed a decentralized, autonomous state estimation algorithm for SmallSats that provides PNT service using terrestrial GPS pseudoranges and inter-satellite communication links.…”

Satellite Constellation Design for a Lunar Navigation and Communication System

“…In prior works (Bhamidipati et al, 2021(Bhamidipati et al, , 2022a, we proposed the design of a SmallSat-based lunar navigation satellite that utilizes available Earth-GPS signals (when not occluded by Earth or the Moon) to estimate the timing corrections of a lower-grade satellite clock. A formulation of a lunar UERE was devised that primarily depends on the root-mean-square (RMS) timing error in the time transfer from the Earth GPS.…”