Minimize ORS-5

ORS-5 (Operationally Responsive Space-5) / SensorSat

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The USAF (U.S. Air Force) officials have approved the ORS-5 bridging mission for launch in 2017 to monitor satellite traffic in geosynchronous orbit, tasking the MIT/LL (Massachusetts Institute of Technology /Lincoln Laboratory) to design and build a small space surveillance satellite. The ORS-5 mission, also known as SensorSat, is managed under the auspices of the USAF /ORSO (Operationally Responsive Space Office) based at Kirtland Air Force Base, N.M. 1) 2)

The Air Force's space surveillance network incorporates data from ground-based radars, SBSS (Space-Based Surveillance System) and other assets to keep tabs on more than 23,000 objects in orbit. The ORS-5 program will demonstrate a low-cost small satellite launch capability and aspects of autonomous operations via the existing Multi-Mission Space Operations Center ground architecture.

The overall objective of ORS-5 is to to continue the SBSS satellite program's mission to detect, track, and identify objects in deep space. These capabilities are needed to give satellite operators actionable knowledge and the ability to leverage U.S. and allied space capabilities to protect space assets and counter any potential hostile space activities. The ORS-5 mission is to answer a JFC (Joint Force Commander) need for SSA (Space Situational Awareness) of the geosynchronous (GEO) belt. The goal of the ORS-5 program is to demonstrate technologies that could prove "good enough" for geosynchronous SSA, create risk reduction opportunities to a future program of record, and develop and demonstrate ORS enablers and principles. 3)

In addition, the ORS-5 mission will act as a pathfinder for technologies to be used in a follow-on to the current SBSS-1 (Space Based Space Surveillance-1) satellite. ORS-5 provides risk reduction for cutting-edge technologies to be transitioned to the SBSS Follow-On program. ORSO will execute a technology transfer strategy, seeking opportunities for early industry involvement through requests for information and a near-term industry day.

The ORS-5 approach combines a streamlined commercial launch acquisition strategy, combined with a tailored systems architecting and mission assurance process for faster development outcomes in both ground and space segments. The ORS-5 mission is an "operational demonstration" that will provide continuous observation of the geosynchronous earth orbit (GEO) belt for the purposes of SSA. Highly unique to the mission is use of low-earth orbit, equatorial small satellite viewing of the GEO belt with a flight geometry and sensor arrangement that allows uninterrupted observations throughout its nominal 104 minute synodic orbit. 4)



The ORS-5 integrated space vehicle is being designed, built, integrated and tested by MIT Lincoln Laboratory (MIT/LL). Lincoln's history of developing visible CCD (Charge Coupled Device) sensors with high sensitivity was the primary driver for the award as well as the "urgent need" nature of the program. The vehicle design is a highly integrated package with a mass of ~120 kg and a length of 1.5 meters, whereby vehicle components and actuators are placed optimally around the stray light baffle, lens assembly, camera system that comprise the vehicles sensor. The most highly unique attribute of SensorSat is the combined use of the TDI (Time Delay Integration) technique in the sensor's camera system and a flight geometry, that when combined, allow a continuous imaging and readout of the sensor for non-stop imaging of the GEO belt.

The space vehicle components are all commercial space vendor supplied except for the sensor's CEB (Camera Electronics Board ) which is solely Lincoln Laboratory designed and built. MIT/LL designed all spacecraft bus structural panels, sensor optics, stray light baffle, CCD mount/camera assembly and camera radiator assembly. The EDU (Engineering Development Unit) components were either built or acquired for every space vehicle component and the EDU space vehicle is key to Lincoln's functional, performance and environmental stress screening risk reduction ahead of final flight vehicle build and test.

SCD (System Capability Demonstrations): Key attributes applied to the ORS-5 program are the use of SCDs, "just in time" development of engineering drawings and assembly/test procedures and the high use of EDU vehicle components. Identified as part of the acquisition strategy, SCDs are part of developing the program's functional architecture and planned as risk reduction events using both hardware and simulations to show progress and likelihood of success for key ORS-5 attributes. SCDs enabled a much lower level of formal "insight/oversight" activities more typical of other military operational programs (Figure 1).


Figure 1: ORS-5 SCDs (Systems Capabilities Demonstrations), image credit: USAF /ORSO)

SCD-1 was completed successfully in January 2015 and was aimed at demonstrating MIT Lincoln Laboratory's preliminary designs of critical and enabling system elements could meet system functional and performance requirements for preliminary avionics control system and image processing chain including sensor-in-the-loop-control. Using emulated system sensors, actuators, and a high-fidelity physical models the demonstration used representative hardware to the maximum extent possible, along with derived characterizations of actual hardware to help validate preliminary system models. It provided insight potential system weaknesses and performance margins on system components, both hardware.

SCD-2 was used as a primary risk reduction test for the sensor subsystem, testing functional prototypes to provide feedback to EDU/Flight design efforts and serve as a preliminary design vector check between PDR (Preliminary Design Review) and CDR (Critical Design Review). The primary objectives of SCD-2, successfully completed in May 2014 were to validate optical performance of the OTA (Optical Telescope Assembly) to include optical throughput, focal plane distortion, ensquared energy at the focal plane, a-thermal performance, and structural integrity verification. Additional objectives included validating stray light performance against ray tracing analysis, demonstrating the end-to-end photon to digital chain and affirming the design maturity of a prototype optical telescope, stray light baffle and functional prototype camera electronics.

SCD-3 was an integrated system (Flat Sat) demonstration to validate the SensorSat FSW (Flight SoftWare) and GNC software functions and interactions with the complete complement of EDU hardware sensors and actuators. SCD-3 was successfully completed in August 2015 and demonstrated end-to-end performance of image-based pointing control loop, as well as real-time execution of algorithms on flight processor hardware. SCD-3 further demonstrated compatibility of hardware to software GNC interfaces (Full I/O set), the ability of the GNC hardware and software to respond appropriately to a simulated tumble to stabilize the SensorSat in Coarse Pointing, the ability of the GNC hardware and software to maintain stable SensorSat pointing with sensor-in-the-loop Fine Pointing and the ability of the flight software and firmware to process sensor image data.

MA (Mission Assurance): Mission assurance for ORS-5 given the small program size and budget relies on point application of subject matter expertise against early identified areas of risk or questions. Aerospace Corporation, Space Dynamics Laboratory, MITRE, Applied Physics Laboratory, all part of a ORS developed FFRDC/UARC (Federally Funded Research and Development Centers/University Affiliated Research Centers) consortium are called upon to witness key events such as SCD-3's for independent insight to system development activities. Also key to the MA roles is the use of ORS program office "embedded" presence at vendor facilities, most notably at MIT Lincoln Laboratory. ORS-5 has the promise to radically change the way future GEO belt space situational awareness is conducted. The ORS-5 system design is currently being discussed as the governments "reference design" for the follow-on program to SBSS program of record. The unique TDI technique and the optimized flight geometry attributes combine to allow low-cost, relatively simple, non-propulsive small satellites to fulfill a key SSA mission. ORS-5 success will further to establish ORS principles as viable alternatives to traditional space mission fulfillment.


Launch: The launch of the ORS-5 spacecraft is scheduled for July 2017. In July 2015, Orbital ATK was awarded a contract from the USAF to launch ORS-5 in 2017. The launch vehicle for ORS-5 is the Minotaur-4 vehicle. The launch site is the Cape Canaveral Air Force Station, SLC-46 (Space Launch Complex-46), Cape Canaveral, FL. 5)

Orbit: Circular equatorial orbit, altitude of 625 km, inclination = 0º.

Flying in an Earth-centered fix (ECF) attitude at what is known as the "magic angle," the ORS-5 vehicle images at a rate at which celestial objects are fixed and can be discerned from RSOs (Resident Space Objects) at geosynchronous altitude. Re-imaging of the entire GEO belt from an altitude of 625 km each 104 minute orbit allows a high awareness of change activity in the belt. The non-propulsive space vehicle is designed to use "sensor in the loop" as part of its fine pointing capability and the vehicle attitude over its lifetime will be adjusted to maintain the "magic angle" as a function of orbit altitude.


Figure 2: The ORS-5 mission concept (image credit: USAF /ORSO)



Sensor complement

The SensorSat payload will circle the planet in LEO (Low Earth Orbit) to scan the valuable region of space 35786 km high — the geosynchronous orbital belt — to spot debris and warn against collisions. GEO (Geosynchronous Earth Orbit) is where communications satellites, weather observatories and key reconnaissance platforms reside because that altitude allows the craft to fly continuously above the same part of the globe. 6)

Many of the details about ORS-5 remain classified. But SensorSat will test technologies and reduce the risk for future SSA (Space Situational Awareness) missions.

MIT/LL (Massachusetts Institute of Technology/Lincoln Laboratory) developed systems to detect, track, and identify man-made satellites; collects orbital-debris detection data to support spaceflight safety; performs satellite mission and payload assessment; and investigates technology to improve monitoring of the space environment, including space weather and atmospheric and ionospheric effects. The technology emphasis is the application of new components and algorithms to enable sensors with greatly enhanced capabilities and to support the development of net-centric processing and decision support systems. 7)


Figure 3: Flight-like hardware subsystems for SensorSat were integrated and tested as part of a system capability demonstration. Seen here is the imaging system, which consists of a Lincoln Laboratory–developed CCD imager, camera electronics, a custom lens cell, and a state-of-the-art lightweight baffle (image credit: MIT/LL)



Ground segment:

The ORS-5 mission is designed for 3-years on orbit and will undergo a rapid launch and early operations (LEO) checkout before transitioning into operational transition/"trial period." Operations of the system will initialize at the Kirtland AFB, RDT&E (Research, Development, Test and Evaluation) Support Center for the launch and early orbit "checkout" portion of on-orbit operations and then will transition to Schriever AFB for operational capability thereafter.

Operations of the ORS-5 vehicle will be conducted using the MMSOC (Multi-Mission Space Operations Center) ,version 2.1, located at 1st Space Operations Squadron and employing the use of Lincoln Laboratory developed mission unique software on the "Neptune" common ground architecture operation system. Lincoln Laboratory is responsible for mission data processing and will use an ORS-5 specific update of their previously developed OPAL (Optical Processing Architecture at Lincoln) software.

Command and control of ORS-5 will be done in both developmental and operational phase's on-orbit through the AFSCN (Air Force Satellite Control Network ). Due the unique nature of a low Earth, equatorial orbit, only 3 AFSCN stations are geometrically in line-of-sight to the ORS-5 satellite. Guam and Diego Garcia AFSCN locations are primary and backup ground stations with Hawaii's station having very limited capability as a backup in the case of lost contact with the primary station.


1) Stephen Clark, "Air Force satellite to continue tracking of space traffic," Spaceflow Now, Sept. 3, 2014, URL:

2) "New Mission Selected for Operationally Responsive Space Office," Los Angeles Air Force Base, July 30, 2014, URL:

3) Thomas M. Davis, "Operationally Responsive Space – The Way Forward," Proceedings of the 29th Annual AIAA/USU Conference on Small Satellites, Logan, Utah, USA, August 8-13, 2015, paper: SSC15-VII-4, URL:

4) Thomas M. Davis, Peter J. Thomas, Darrell B. Story, "Sall satellites for operationally responsive space," Proceedings of the 4S (Small Satellites, System & Services) Symposium, Valletta, Malta, May 30-June 3, 2016, URL:

5) Mike Gruss, "Orbital ATK Chosen To Launch U.S. Air Force's ORS-5 Satellite," Space News, July 3, 2015, URL:

6) Justin Ray, "Teams practice for Cape Canaveral's first launch of Minotaur 4 rocket," Spaceflight Now, Feb. 12, 2017, URL:

7) "Space Control," MIT/LL, URL:

The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: "Observation of the Earth and Its Environment: Survey of Missions and Sensors" (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates (

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