Technical note | Modelling a C-Band Space Surveillance Radar using Systems Tool Kit

Abstract

 A model of the AN/FPQ-14 C-Band radar was developed using Analytical Graphics, Inc. (AGI) STK software to support studies investigating the operational performance of the system for surveillance of Space and the contribution it could make to the Space situational awareness mission. STK scenarios were developed to assess the detection performance of the radar model against a satellite target with a given orbital altitude, radar cross section (RCS) and minimum signal to noise ratio (SNR) required for detection. These results were compared to those obtained by evaluating the radar range equation. A comparison was also made on the effects of refraction using the effective radius method and International Telecommincations Union (ITU) model.

Executive Summary

The US Space Surveillance Network (SSN) is a collection of sensors dispersed around the world for surveillance of Space. These sensors are used to detect, track, identify and characterise objects in Space such as payloads, rocket bodies and debris to provide Space situational awareness information.

The AN/FPQ-14 is a conventional (dish) radar used for surveillance of Space. This radar operates in the C-Band (5.4 to 5.9 GHz) and can provide very accurate tracking information on objects in Space, however it can only track objects within a very narrow beam and requires cueing to the target.

In order to support studies investigating the operational performance of the AN/FPQ-14 radar for Space surveillance and assess the contribution it can make to the Space situational awareness mission, a model of the radar was developed using Analytical Graphics, Inc. (AGI) Systems Tool Kit (STK) software.

STK formerly known as Satellite Tool Kit, is a computer software suite for modelling, analysing and visualising Space, defence and intelligence systems. The software can be used to develop high fidelity models and simulations of complex systems such as aircraft and satellites as well their sensors and communications. It includes an add-in module specifically for detailed analysis and visualisation of radar systems, STK/Radar, which has been extensively used in this work.

The radar is modelled as an object in STK by defining basic parameters including: mode of operation, frequency, peak power, antenna setup, system temperature and other gains and losses. Fidelity of the model is increased by considering additional advanced settings available in STK/Radar. These include modelling of pulse integration modes required to simulate tracking of targets. The effects of refraction are also taken into consideration.

A STK scenario was created to assess the detection performance of the radar model against a satellite target with a given orbital altitude, radar cross section (RCS) value and minimum signal to noise ratio (SNR) required for detection. STK computes 'access' (i.e. visibility from one object to another based on constraints placed on them in the scenario) from the radar to the target and outputs the azimuth, elevation and range when it is being tracked.

The STK detection performance results for the radar were compared to those obtained from a simple analysis that determined the detection range of objects with a given radar cross section (RCS) using the estimated operating characteristics of the radar input into the radar range equation which has been reported in previous work. A comparison was also made on the effects of refraction using the effective radius method and International Telecommunications Union (ITU) model.

The results showed that for a given minimum SNR required for detection of 15 dB, which based on previous analysis appeared to closely match what was known about the operating performance of the radar, orbital objects with a 1 m² RCS (considered to be representative of a payload) can be detected out to the radar horizon at an orbital altitude up to about 500 km, whereas detection of much larger objects, e.g. boosters with a 40 m² RCS, are horizon limited regardless of the orbital altitude for objects in LEO. Detection of small payload size objects and smaller ones (less than 0.1 m²) will be limited by the performance of the radar and debris with an average RCS less than or equal to 0.01 m² are unlikely to be detected at the higher LEO altitudes (above about 1200 km).