Abstract

During the entire launch sequences from liftoff to final orbital insertion of a space vehicle (SV), adequate link requirements are to be maintained for telemetry, tracking, and command (TT&C) for uplink and downlink services, from launch vehicle (LV) and SV to ground stations (GS). A successful space vehicle launch required adequate link coverage with good radio frequency (RF) performance. The chapter is an extension of the IEEE/Aerospace Conference 2019 paper entitled Dynamic Link Analysis and Application for a MEO Space Vehicle published by the authors. The emphasis in this chapter is on the addition of the three distinctively different tracking waveforms and their associated links, used from liftoff to final orbital insertion. This chapter will describe the three required dynamic link analyses (DLA) to cover (a) the LV link from liftoff to its end of line of sight (LOS), (b) the LV link from LOS to Tracking and Data Relay Satellite System (TDRSS) at beyond line of sight (BLOS), and (c) the final tracking link using Space-to-Ground Link Subsystem (SGLS) or non-SGLS (NSGLS) link for the earliest or best separation time of the SV from the LV. The chapter discusses the concept of the dynamic link analysis, SV antenna switching schedule, recommended SV separation time, as well as the performance for different launch scenarios within the 24-h launch window. Topics include antenna patterns, launch trajectories, elevation angle and clock and cone angle geometry, and dynamic link budget.

Highlights

  • There was an interest to extend the present dynamic link analyses (DLA) beyond the early launch period to cover the period after the space vehicle (SV) separation from launch vehicle (LV), which includes both booster and second stage engine

  • This transmit system will be consisting of a high-power amplifier (HPA) which amplifies the signal to generate an output power expressed in dBW (conversion from Watts to dBW is dBW = 10*log10(Watts)); some cables and circuits with a loss and an antenna with a gain are added together as shown below

  • The system temperature is the sum of antenna sky temperature (TA) and the composite temperature from antenna line loss (LL) and low noise amplifier noise figure (NF) which are referred to the antenna feed

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Summary

Introduction

There was an interest to extend the present dynamic link analyses (DLA) beyond the early launch period to cover the period after the space vehicle (SV) separation from launch vehicle (LV), which includes both booster and second stage engine. The purpose of the dynamic link study for the launch is to provide the earliest and accurate time for final SV separation and orbital insertion as compared to previous method which only relied on visibility tracking coverage to the end of line of sight (LOS). From the end of LOS to BLOS, the tracking telemetry link is usually a BPSK or QPSK signal, using a NASA Tracking Data Relay Satellite System to relay tracking data from the LV to White Sands or Goddard ground station (WSGT/GRGT) and routing it to other user ground stations. In the following pages, supporting link analyses for the two LV and one SV tracking stages will be presented

Antenna coordinate system definition
Dynamic link formulas of interest
Tracking signals and link analyses along the trajectory
Basic link parameters and formulas
Transmission medium and losses
Received isotropic power
Receive system and performance
Space vehicle link services
SNR and link margin calculation
Launch vehicle dynamic link
Findings
Conclusion
Full Text
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