Elsevier

Advances in Space Research

Volume 60, Issue 12, 15 December 2017, Pages 2723-2732
Advances in Space Research

In-flight performance analysis of MEMS GPS receiver and its application to precise orbit determination of APOD-A satellite

https://doi.org/10.1016/j.asr.2017.08.023Get rights and content

Abstract

An experimental satellite mission termed atmospheric density detection and precise orbit determination (APOD) was developed by China and launched on 20 September 2015. The micro-electro-mechanical system (MEMS) GPS receiver provides the basis for precise orbit determination (POD) within the range of a few decimetres. The in-flight performance of the MEMS GPS receiver was assessed. The average number of tracked GPS satellites is 10.7. However, only 5.1 GPS satellites are available for dual-frequency navigation because of the loss of many L2 observations at low elevations. The variations in the multipath error for C1 and P2 were estimated, and the maximum multipath error could reach up to 0.8 m. The average code noises are 0.28 m (C1) and 0.69 m (P2). Using the MEMS GPS receiver, the orbit of the APOD nanosatellite (APOD-A) was precisely determined. Two types of orbit solutions are proposed: a dual-frequency solution and a single-frequency solution. The antenna phase center variations (PCVs) and code residual variations (CRVs) were estimated, and the maximum value of the PCVs is 4.0 cm. After correcting the antenna PCVs and CRVs, the final orbit precision for the dual-frequency and single-frequency solutions were 7.71 cm and 12.91 cm, respectively, validated using the satellite laser ranging (SLR) data, which were significantly improved by 3.35 cm and 25.25 cm. The average RMS of the 6-h overlap differences in the dual-frequency solution between two consecutive days in three dimensions (3D) is 4.59 cm. The MEMS GPS receiver is the Chinese indigenous onboard receiver, which was successfully used in the POD of a nanosatellite. This study has important reference value for improving the MEMS GPS receiver and its application in other low Earth orbit (LEO) nanosatellites.

Introduction

The atmospheric density detection and precise orbit determination (APOD) is an experimental satellite mission for precise orbit determination (POD) and thermosphere density detection, developed by China and launched on 20 September 2015. The APOD comprises one nanosatellite named APOD-A with a mass of 15 kg and three identical picosatellites with a mass of 5 kg in a near-circular orbit with an inclination of 97.4° and an altitude of 530 km. After commissioning, the APOD-A performed orbit manoeuvring to reduce the orbit altitude to 460 km through multiple thrusting by 27 October 2015. The payloads equipped on the APOD-A include a micro-electro-mechanical system (MEMS) GPS receiver, an atmospheric density detector, an SLR reflector, and an S/X VLBI beacon. An ionisation gauge is used as the atmospheric density detector to measure the atmospheric pressure and temperature. Space-borne global navigation satellite system (GNSS) observations have been widely used in atmospheric sounding (Jin et al., 2011). The MEMS GPS receiver delivers data with a dual-frequency of 0.125 Hz and provides the basis for the POD of the APOD-A within the range of a few decimetres. The obtained precise orbit, which can be used to independently validate the accuracy of the atmospheric density detector (Sang et al., 2012, Calabia and Jin, 2017), would give great help for the later atmospheric density detection.

Space-borne GNSS receivers have become the most important equipment for the POD of low Earth orbit (LEO) satellites. Many efforts have been made to obtain precise orbits of the LEO satellites up to several centimetres using non-MEMS GNSS receivers (Kang et al., 1995, Ijssel et al., 2003, Haines et al., 2004, Jäggi et al., 2007). Over the last fifteen years, the small-satellite industry experienced an explosive growth, most of which coming from the nanosatellites (Armen and Alessandro, 2017). For the LEO nanosatellite navigation, the MEMS GPS receivers are quite significant in that they are smaller and cheaper. The MEMS is obtained by integrating mechanical elements, sensors, actuators, and electronics on a common silicon substrate using microfabrication technology. The MEMS GPS receivers have received significant attention owing to low inherent cost, small size, and low power consumption (Park and Gao, 2008). However, their performance needs to be verified for high-precision applications such as space missions. In this study, the in-flight performance of the MEMS GPS receiver is assessed, and the POD of the APOD-A is performed. The results of our study contribute to a better understanding and possible improvement of the MEMS GPS receiver.

With the improving accuracy of the POD, neglected or mismodelled antenna phase center variations (PCVs), which can be attributed to ground calibrations, multipath errors, and in-flight environment, have gradually become one of the most important error sources of carrier phase observations in LEO GPS data processing. In-flight calibration of the receiver antenna PCVs has been employed for many satellites, such as Jason-1 (Luthcke et al., 2003), GRACE (Montenbruck et al., 2009, Jäggi et al., 2009), TerraSAR-X (Montenbruck et al., 2009, Wermuth et al., 2011), COSMIC (Hwang et al., 2009), GOCE (Bock et al., 2011), Haiyang 2A (Guo et al., 2015), Shiyan 3 (Gu et al., 2016). In addition, antenna code residual variations (CRVs) are similar effects on the code observations (Kersten and Schön, 2016), which is also necessary to be calibrated, particularly for single-frequency GPS applications. In this study, the PCVs and CRVs of the antenna of the MEMS GPS receiver were estimated, and their effects on the POD of APOD-A were analysed. The MEMS GPS receiver payload is a state-of-the-art Chinese indigenous space-borne receiver, which has been successfully used for the POD of a nanosatellite, and will be used for future LEO nanosatellite navigation.

Section snippets

Ability of tracking multi-channel GPS satellites

The ability of tracking multi-channel GPS satellites is analysed. Fig. 1(a) and (b) show the views of the distributions of L1 and L2 observations with respect to the elevation and azimuth in the antenna reference frame (ARF). Significant differences exist between the L1 and L2 observations in receiving the GPS signal. The minimum elevation can reach up to −20° for L1, whereas it is only 10° for L2. This indicates that more tracking losses occur in L2 observations than that in L1 observations.

Precise orbit determination for APOD-A

The MEMS GPS receiver equipped on the APOD-A provides dual-frequency observations. The orbital accuracy of the single-frequency solution is usually poorer than that of the dual-frequency solution. However, the orbital accuracy of the single-frequency solution is still worthy to be analysed in this study because the observation quality of the L1 frequency of the MEMS GPS receiver is much better than that of the L2 frequency. Moreover, the study can contribute to a better understanding of other

Conclusions

In this study, the in-flight performance of the MEMS GPS receiver was assessed and its application in the POD of the APOD-A satellite is analysed. The main conclusions of this study are as follows.

(1) The average number of tracked GPS satellites is 10.7; however, only 5.1 GPS satellites are available for dual-frequency navigation because of the loss of many L2 observations at low elevations. The variations in the multipath error for C1 and P2 observations are estimated, the maximum value of

Acknowledgments

The authors would like to thank the Beijing Aerospace Control Center and ILRS for providing the GPS observations and the SLR data of the APOD mission. This study was co-supported by the National Natural Science Foundation of China (Nos. 61370013 and 91438202). In addition, the authors would like to thank the reviewers for their valuable remarks that helped to improve the original manuscript.

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