Impact of flex power on GPS Block IIF differential code biases
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ORIGINAL ARTICLE
Impact of flex power on GPS Block IIF differential code biases Özge Gizem Esenbuğa1 · André Hauschild1 Received: 24 March 2020 / Accepted: 4 June 2020 © The Author(s) 2020
Abstract GPS Block IIF satellites are able to redistribute the transmit power between the signal components. This ability is called flex power, and it has been developed as a remedy against jamming. Since it is operationally not possible to increase the transmit power for all signal components simultaneously, a redistribution between them is necessary under certain operational situations. Flex power has been active on Block IIF satellites since January 2017 over a specific regional area and has an impact on differential code bias estimation as well as the signal-to-noise density ratio. A network of the International GNSS Service stations containing only Septentrio PolaRx5 and PolaRx5TR receivers between August 1 and November 21, 2019 has been used for differential code bias estimation using GPS L1 C/A, L1 P(Y), L2 P(Y), and L2C signals with and without consideration of the flex power in the estimation process for Block IIF satellites. The estimation results are compared with the German Aerospace Center as well as the Chinese Academy of Sciences DCB products to validate the results. Keywords Differential Code Biases · Flex Power · GPS Block IIF
Introduction The Block IIF satellites are the fourth generation of the GPS satellites. These satellites provide the new L5 signal in addition to the legacy GPS L1 C/A code, L1/L2 P(Y) code signals, the civil L2C signal on L2, and the military M code on L1/L2. The motivation for launching the Block IIF satellites was replacing failed satellites using the so-called “launch on need” approach (Fisher and Ghassemi 1999). The first Block IIF satellite was launched in May 2010 (Federal Radionavigation Plan 2019). There are in total 12 different Block IIF satellites in operation. All GPS satellites normally transmit their signal with constant total power and constant power ratios between the different signal components. Nevertheless, Block IIR-M and Block IIF satellites are able to redistribute the transmit power between L1 and L2 signals individually (Rajan and Tracy 2002). Owing to the adjustable power output capability, the individual signal components of Block IIR-M and * Özge Gizem Esenbuğa [email protected] André Hauschild [email protected] 1
Deutsches Zentrum für Luft- und Raumfahrt, German Space Operations Center, 82234 Wessling, Germany
Block IIF satellites can exceed their pre-defined maximum value. However, this value is not expected to exceed -150 dBW under certain operational situations (IS-GPS-200K 2019). The ability to redistribute the transmit power is called flex power. There are different kinds of flex power modes that have been studied so far (Steigenberger et al. 2018). The flex power mode discussed here is the one that is empowered since January 2017 on the Block IIF satellites, and its signature is a power increase by 2.5 dB-Hz of the L1 C/A and P(Y) signal
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