Military Technology 05/2021

An artist’s impression of the HBTSS role in tracking an HGV during its re-entry and glide manoeuvres. Note that the Next Generation Geo-stationary (NGG)/ Next Generation Polar (NGP) and the Space-Based Infra-Red Satellite (SBIRS)/Defense Support Programme (DSP) constellations undertake the initial detection, characterisation and cueing function. (Photo: Northrop Grumman) System (HBTSS) programme. HBTSS will deploy a constellation of low earth orbit (LEO) satellites, fit- ted with new sensor payloads that can search for, track and communicate data on an HGV’s position and route to headquarters or coordination centres on the ground. HBTSS is being developed in collaboration with the US Space Force under the leadership of the Chief of Space Operations and the Space Development Agency (SDA). It will be part of the wider US air and missile defence network, and will integrate with it, adding to its existing capabilities. Once a ballistic missile launch is detected, the ex- isting missile warning satellite sensor network will cue the HBTSS constellation onto the target for tracking of the post-burn- out phase of the HGV’s journey. Mark Wright, Director of Public Affairs at the MDA, told MilTech that HBTSS is being developed “<I>as a unique Overhead Persistent Infra- Red (OPIR) sensor, providing fire-control quality tracking data on hyper- sonic threats and ballistic missile threats. HBTSS will provide low-laten- cy critical data to the Missile Defense System and support Combatant Command needs associated with advanced threats. Ultimately, this data is critical to enabling engagement by missile defense weapons, including engagement by glide-phase weapons.” By operating in LEO, the satellites will be best placed to see HGVs, since they can look upwards into space at any HGVs going overhead and are also physically much closer to them. This makes it easier for the sen- sors to spot the HGVs, because the picture will be set against a dark, cold background. IR sensors fitted to higher altitude satellites, on the other hand, would be looking down at the Earth, making it more difficult to identify and track the dimmer signature of the HGV among the ‘clutter’ of the Earth – heat, light and all the human and natural movements. In January 2021 the MDA awarded Other Transaction Authority (OTA) contracts to L3Harris Technologies for $122 million ( € 103.4 million) and Northrop Grumman ($155 million) for the HBTSS Phase IIb On-orbit Prototype Demonstration. These two companies were down-selected from an earlier group of four that also included Raytheon Technologies and Leidos. The quartet had each been working under $20 million Phase II study contracts to develop a new payload, and also completed a ground test-bed and preliminary design review (PDR). Wright said that, under Phase IIb, the designs will be matured further and “will result in launch and early orbit testing of HBTSS prototype satellites that demonstrate the sensitivity and fire-control quality of service necessary to support both the emerging hypersonic threat kill chain and detection of dim upper stage missiles.” The current Phase IIb contracts will take the work on HBTSS from the PDR stage through to prototype system delivery, and two satellites are expected to be deployed in FY 2023. Wright explained that “The goal is to deploy an operational prototype system that will provide a rapid capability The development of hypersonic glide vehicles (HGVs) represents a serious threat – the threat of new weapons, potentially extending the reach of a nation’s unmanned offensive firepower to intercon- tinental ranges. Already the case, of course, for countries operating ballistic missiles, but HGVs offer a unique attribute – the ability to avoid detection by evading existing ground-based radar networks and space-based sensors. Although HGVs are launched using an intercontinental ballistic missile (ICBM) as a boost vehicle, they separate at burnout to enter the upper at- mosphere at about 100km altitude. It then performs a re-entry manoeuvre, gliding back down to earth and reaching hypersonic speeds, provid- ing the kinetic energy that delivers its destructive power. A shuttle-like shape, featuring stabiliser wings means that the HGV can change direc- tion, taking less predictable routes and manoeuvring onto a target more dynamically than would otherwise be possible. Because HGVs do not follow a ballistic trajectory, current air and mis- sile defence warning systems that track ICBMs, typically out to 200km, will lose contact. Furthermore, as HGVs do not use use a booster, they display a much dimmer heat signature for existing Infra-Red (IR) sensors to detect. Without the ability to find HGVs, a frightening prospect rears its head: the potential for these weapons to hit strategic targets, such as military bases or industrial centres – or deployed forces on land or at sea – with little or no prior warning. For the West, examples of such threats include Russia’s development of the AVANGARD HGV (carried on the SS-19 ICBM) and China’s DF-ZF HGV programme (carried on the DF-17 ICBM). Both are also nuclear-ca- pable, and would be able to penetrate existing air and missile defence networks. Enter HBTSS To provide an HGV detection capability, the US Missile Defense Agency (MDA) is engaged in the Hypersonic Ballistic Tracking and Surveillance Tim Fish The Hypersonic Era – Threat and Countermeasures f 48 · MT 5/2021 · Special Supplement Military Space