Return of the pioneering solution – Pegasus mission scheduled on 2016

Orbital ATK has scheduled mission utilizing their first launch system, Pegasus. It will lift to LEO orbit satellite under Cyclone Global Navigation Satellite System (CYGNSS) program. Launch is planned for October 2016.

After three years of pause in Pegasus mission, Orbital ATK will utilize their air-launched rocket in commercial mission. It will be, contracted with NASA, launch of their new satellite designed for ocean observation and hurricane forecasting. NASA is still interesting in developing their constellation of various weather satellites. CYGNSS is result of cooperation with the University of Michigan, Southwest Research Institute of Texas, Surrey Satellite Technology of Colorado and NASA Ames Research Center. Program started in 2012 with NASA donation of $152 million and with ambitious aim of creating fleet of eight weather forecasting satellites. Pegasus will be equipped with special deployment module made by Sierra Nevada Corporation. It will be a tube with two rows of four satellites inside. Every pair of satellites will be starting from module in opposite directions with speed at 1 m/s. Planned orbit for satellites is about 500 km and three years, after reaching end of the operational life, all satellites should burn in atmosphere to avoid creating space debris. Each satellite is built by Southwest Research Institute. GPS system necessary for correct research is provided by USA division of Surrey Satellite Technology Ltd; solar panels for satellites will be designed and manufactured by EMCORE. Satellite is manufactured from CNC milled Aluminum with bolted parts and combined with combined with honeycomb structure. Mass of satellite is low, at 27.5 kg; it will make possible to launch eight satellites and deployment module in one mission (Pegasus is limited with 443 kg payload capacity). Satellite is equipped with Thermal Control System (for active cooling control), ADCS (Attitude Determination and Control Subsystem) for steering and stability control, EPS (Electrical Power Subsystem) providing battery charging without jamming and interrupting of observation systems (power required for operating is at 38.3 W) and S band transceiver for communication with 4 Mbit/s downlink/2 Kbit/s uplink data rate. Scienctific equipment will be mainly DDMI (Delay Doppler Mapping Instrument) responsible for measuring surface of ocean. It works utilizing scattered from GPS satellites signals to create DDM (Delay Doppler Map) and has possibility of accumulating up to 60 seconds of raw sampled data. Receiver and three antennas of DDMI are designed and manufactured by Surrey Satellite Technology US LLC.

Pegasus is oldest launch vehicle by Orbital ATK. It was presented in 1990 as air-launched rocket for LEO missions. It was developed mainly for small satellites, due its payload capacity with diameters 1.18 by 2.13 meter with maximum weight at 443 kg. It is known as first winged vehicle able to reach 8 Ma and first privately designed and manufactured launch vehicle. Launching of the rocket starts with using special modified plane called Stargazer L-1011.  After reaching height of 12000 m rocket is dropped from plane and after about 5 seconds solid fueled Orion 50S engine is turning on. On 61000 m first stage with wings and tail is falling off, after Pegasus reaching hypersonic speed. Second stage engine, Orion 50 is turning on with stabilization in pitch and yaw with roll control provided by third stage nitrogen thrusters. After 1 minute and 18 second second stage is falling with fairing.  Pegasus is in almost vacuum altitude and turns on Orion 38 engine for 64 seconds. After third stage, optional fourth stage equipped with Hydrazine Auxiliary Propulsion System (HAPS is based on three restartable thrusters powered by hydrazine) is activating. Pegasus is reaching LEO and is ready for putting payload into orbit.

Pegasus has many advantages comparing to rockets. It is more independent from weather during start (rocket is starting at 12000 m where meteorological conditions are stable); it is less expensive comparing to traditional rockets. It is not requiring launch facilities, there is no risk of explosion during start. Stargazer is able to start from runways, whole system is easy in transporting.  Main disadvantage is small payload capacity and ability for reaching only LEO. But still, rockets designated for lifting small payloads have often identical drawbacks.  After twenty years of service it proved to be reliable solution. Maybe after failure of railed-launched Super Strypi rocket Department of Defense and U.S. Air Force will look favorably on Pegasus.