The System Engineering process to ensure quality and successful functionality of DubaiSat-2
Date : 19-07-2012
Twenty Emirati space engineers are in the final stages of launch preparation, tests and simulations of DubaiSat-2, the second satellite to be launched by Emirates Institution for Advanced Science and Technology (EIAST).
Testing and evaluation of components of DubaiSat-2, particularly the complex software, is in the final stage, a process known as Flight Model (FM) testing. In the aerospace industry, three-stage testing is the norm for advanced systems. In the first stage, a fully functional Engineering Model (EM) of the satellite and its payload are constructed. Using the EM, engineers put all of the subsystems and their components through their paces, often surpassing normal performance requirements in order to find potential faults.
“During the EM stage of DubaiSat-2 we found numerous problems,” explains Mohammed Al Harmi, the Director of EIAST’s Ground Services Department. “That’s what we want, that’s the purpose of the EM testing stage. We want to know where the problems are before we move to the next step, so we can solve the problems.”
During the EM stage, DubaiSat-2 was put through a battery of tests and simulations to ensure the satellite and its subsystems are able to withstand the rigors of launch and the harsh environment of space. Engineers often exceed the stated specifications for vibration, temperature fluctuations, acoustics and vacuum testing to make sure DubaiSat-2 can withstand everything space can throw at it.
Assistant Researcher, Mohammed Al Abbar says, “All three phases are important to build the satellite. When you reach the FM phase, we reach a level of confidence in the design that has been tested twice already. We might discover new issues or problems during the FM testing, so we need to use the EM or QM module for testing and implementing the new modification to avoid any damage in the FM module. When we get the results that shows that the issues are solved then we can implement it on the FM module and test it for the results.”
Assistant Researcher, Khalid Zowayed explains, “We took the results of the EM stage and went back to the drawing board and modified our plans. When those changes were made, we were ready to move on to the next step in the process, testing the Qualification Model or QM”
“In QM we again put the satellite through the same or even more extreme conditions than it will face in space. It takes about 15 minutes from the moment of liftoff to the time when DubaiSat-2 separates from the launch vehicle, but the stresses and pressures on the satellite are significant. During QM we can ensure that all of the complex subsystems will function properly. In aerospace we don’t like surprises,” said Mohammed Al Harmi.
“Of course the actual launch is only part of the equation,” Al Harmi adds. “When DubaiSat-2 settles into its orbit around the earth, it will do one complete orbit every 90 minutes. For about two-thirds of that time it will be in front of the sun, and for the remaining 30 minutes, it will be in the shadow of the earth. As a result, the satellite and its components must be able to withstand significant temperature changes and the heating and cooling systems have to function precisely. We are extremely pleased with DubaiSat-2’s performance during QM,” said Al Harmi.
The EM and QM stages were completed in February and Emirati engineers working in South Korea are now in the final stage, known as the Flight Model (FM) testing. “This is the final version of the satellite that will actually go to space,” explains Al Harmi. “Checking out the satellite in the FM stage takes time because we are focusing on the onboard software and the mission control software. The simulations are done in real time, giving us a data stream that will simulate what occurs when the satellite is in orbit.”
When asked to identify the most critical component of the satellite, Al Harmi explains, “All of the components and subsystems are equally important. Although redundancy is built in to the system, we can’t take a chance on any individual component not operating flawlessly. It’s like your car, you can’t say the transmission is more important than the engine. If one of them fails, your journey is over. It’s the same with satellite components; all of them must function flawlessly and communicate with each other.”
DubaiSAT-1 has been in orbit since July 2009 and it has been performing well, beaming high quality images back to the Image Processing Centre in Dubai. The images complement existing Geographic Information System (GIS) databases and enable more efficient monitoring of various environmental changes, and natural hazards, in addition to identifying the quality of water in the Gulf region.
Several technical advances are incorporated in the design of DubaiSat-2. EIAST Assistant Researcher, Khalid Zowayed points out, “There is a significant increase in the speed of the data download from 30 Megabits per second, as is the case in DubaiSat-1, up to 160 Megabits per second. This will allow DubaiSat-2 to capture and transmit a phenomenal amount of imagery per day, from 12,000 square meters (in DS-1) to 17,000 square meters (in DS-2). With these technical improvements, the weight of the satellite is now 300 kg, it’s a two metres in height and 1.5 meters wide,” adds Zowayed.
DubaiSat-2 will orbit at an altitude of 600 km. The orbit path has been changed from an ascending orbit (South to North for DubaiSat-1) to a descending orbit (North to South), which will allow both satellites to work well in constellation, as well as giving better coverage over the UAE. Zowayed explains, “We have designed the satellite to produce higher quality images with a panchromatic resolution of one metre and a multispectral resolution of 4 metres in four spectral bands (Red, Green, Blue and Near Infrared). This will enhance the quality of the images for various applications including environmental projects, urban planning, infrastructure, telecommunications and electricity.”
Assistant Researcher, Khalid Anoohi says, “DS-2 will be using the Hall Effect Propulsion System (HEPS) to maintain the orbit of the satellite. It will be used as an experimental electrical propulsion system, as a start for possible future use of electric propulsion for interplanetary missions. Such a technology is fuel efficient, and can reduce heavily the weight of a launched satellite. This research is expected to support the Space Society in utilizing the technology in the future.
The emphasis during development of DubaiSat-1 was on knowledge transfer to the UAE team working alongside their South Korean counterparts (SATREC Initiative). With DubaiSat-2, the UAE team is involved all aspects of the design, development, manufacturing and subsequent launch.
Salem Al Marri, Head of the Space Program Department at EIAST says, "The UAE team of engineers benefited from their first experiences with DubaiSat-1 as they learned about satellite systems development. By drawing on that experience, they have made significant contributions to DubaiSat-2. Their involvement marks the giant stride that the UAE has made in the path of scientific research and technical progress."
EIAST Director of Space Images Department, Omran Anwar Sharaf believes, "The UAE engineers have acquired experience and knowledge that will enable them to initiate UAE projects to serve the country in the field of space and satellite manufacturing."
Digital Hardware Team Leader, Suhail Al Dhafri says, “EIAST Space Development skills have increased and achieved great advances towards space project development. We want to build the infrastructure of space development in the UAE and increase awareness of space technology throughout our nation.”
Mohammed Al Harmi, the director of Ground Services says, “In the case of DubaiSat-2 we have witnessed a significant increase in the participation of UAE engineers. They are involved in developing solutions, techniques and advanced research, thus contributing directly to the design and applications, in addition to enhanced co-operation with international institutions such as the Japanese Space Agency for introducing new techniques in the satellite.
EIAST has contracted the International Space Company Kosmotras (ISCK) from Russia to launch DubaiSat-2 on board a Dnepr Rocket from Yasny Cosmodrome in Russia. The launch is planned for late November or early December 2012. As soon as DubaiSat-2 is in orbit, the Engineering and Qualification Models will be disassembled and shipped to Dubai. Once reassembled, they will be used to conduct diagnostics and pretest any modifications required on the orbiting DubaiSat-2.
EIAST
