PSLV-C25/Mars Orbiter Mission MARS: The red planet Mars is the only planet of our solar system that remarkably resembles our Earth in many prominent respects. Thus, it is perhaps the best place to search for past or present life outside the Earth. For this reason, Mars has become the target of many unmanned spacecraft from Earth after the dawn of space age in 1957. Mars lies outside the Earth s orbit and revolves round the Sun in an elliptical orbit. Its orbital period is 687 days compared to the Earth s 365 days. Mars takes 24 hours and 39 minutes to spin around its own axis once, which is strikingly similar to a day on Earth. Besides, the axial tilt of Mars is about 25 deg, which is very similar to that of Earth and results in seasons which are about twice as long as those on Earth. For thousands of years, humans have observed Mars in the night sky as a red dot of light moving slowly against the background of fixed stars over a period of weeks. Ancient Romans named it after their god of war because of its red colour. But the orange red colour of the planet is due to the presence of Iron oxide all over its surface. Mars has polar ice caps which consist of solid carbon di oxide as well as water ice which expand and shrink with seasons. Besides, seasonal appearance of dark patches on the surface of Mars made humans to suspect the presence of vegetation on Mars. Strong similarities between Earth and Mars, and, more importantly, optical illusions during the 19 th century telescopic observation of Mars, made humans to suspect the presence of life, especially intelligent life, on Mars. But, robotic spacecraft that have landed on the surface of Mars have not shown any evidence of intelligent life and have not even conclusively detected microbial life there. So, the exploration of Mars through orbiting spacecraft as well as landers and rovers is continuing to seek answers to some of the most fundamental and profound questions about planetary evolution as well as origin and sustenance of life. India s Mars Orbiter Mission is the essential part of the current global effort to understand Mars in greater detail. Today, that effort is mainly focused towards finding out the suitability of Mars in the past to give raise to life and sustain it as well as to search for life on Mars today. This is being endeavoured through both direct and indirect search for Martian life.
Objectives India s Mars Orbiter Mission is more of a Technology Demonstration Mission than a scientific mission. Scientific Objectives of Mars Orbiter Mission: Exploration of surface features, topography, morphology, minerology and atmosphere of Mars through an orbiting spacecraft The main technological objectives of Indian Mars Orbiter Mission are: Design and realisation of a Mars orbiter spacecraft capable of travelling towards Mars, getting into an orbit around that planet and conduct in-orbit observation of Mars Demonstration of the capability to perform deep space communication, navigation, mission planning and management Incorporation of Autonomous features in the spacecraft to handle contingency situations Major Challenges Selection, qualification and incorporation of radiation hardened components in a spacecraft operating in deep space Design and realisation of a spacecraft capable of operating over a wide temperature range near the Earth as well as Mars Ensuring the restart and proper functioning of the Liquid Apogee Motor (LAM) of the spacecraft after a dormant period of 10 months Power management due to reduction in the electric power output of Solar Panels due to lower solar radiation and very low temperatures in Martian orbit Spacecraft communication management in deep space with the associated delay time Incorporation of spacecraft autonomy due to a communication delay time of up to 42 minutes Design, development, testing and qualification of navigation software to accurately send a spacecraft towards Mars and to place it into an orbit around it
The Launch Vehicle The vehicle chosen for launching the 1340 kg Mars Orbiter spacecraft is PSLV-XL, the most powerful version of India s workhorse Polar Satellite Launch Vehicle. This mission to launch Mars Orbiter Mission Spacecraft using PSLV is designated as PSLV-C25 and this is PSLV s twenty fifth flight. PSLV-C25 will be launched from the First Launch Pad at Satish Dhawan Space Centre SHAR, Sriharikota. PSLV-C25 is the fifth flight of PSLV-XL that carries longer and heavier strap-on motors compared to the standard version of PSLV. It stands 44.4 metre tall (fifteen storeys high) and has a lift-off weight of 320 tons. The challenging PSLV-C25 mission is optimised for the launch of Mars Orbiter spacecraft into a highly elliptical Earth orbit with a perigee (nearest point to Earth) of 250 km and an apogee (farthest point to Earth) of 23,500 km with an inclination of 19.2 degree with respect to the equator. It takes about 44 for PSLV-C25 to inject Mars Orbiter Mission spacecraft into that orbit and 37 seconds later, the spacecraft gets separated from the fourth stage of PSLV-C25. Compared to all its earlier missions, PSLV-C25 is very different in one respect since after the separation of its third stage, there will be a long coasting phase of about 25 minutes before the ignition of the fourth stage. This is done to ensure that the spacecraft later achieves minimum energy transfer route from Earth to Mars. Thus, the first phase of Mars Orbiter Mission spacecraft s journey to Mars will be completed in about 44 minutes after lift-off when the spacecraft starts orbiting the earth independently. Since no existing ground station of ISRO Telemetry, Tracking and Telecommand Network (ISTRAC) will have visibility to monitor the ignition and performance of the fourth stage of PSLV-C25 as well as the subsequent spacecraft separation, two ship borne terminals located in the Pacific Ocean will be utilised for monitoring those critical events. This is the first time ship borne ground station terminals are used to monitor an ISRO launch vehicle mission.
PSLV-C25 STAGES AT A GLANCE Stage 1 PSOM-XL Stage 2 Stage 3 Stage 4 Length (m) 20 12 12.8 3.6 2.7 Diameter (m) 2.8 1 2.8 2 2.8 Propellant Solid (HTPB based) Solid (HTPB based) Liquid (UH25 +N 2 O 4 ) Solid (HTPB based) Liquid (MMH+ MON3) Propellant Mass (Ton) 138 12.2 42 7.6 2.5 Peak Thrust (kn) 4800 719 799 247 7.3x2 Burn Time (Sec) 103 50 148 112 525 HTPB : Hydroxyl Terminated Poly Butadiene, UH25 : Unsymmetrical Dimethyl Hydrazine + 25% Hydrazine Hydrate, N 2 O 4 : Nitrogen Tetroxide, MMH : Mono Methyl Hydrazine, MON-3 : Mixed Oxides of Nitrogen Flight Profile of PSLV-C25: Events Time (s) Local Altitude (km) Inertial Velocity (m/s) Mars Orbiter Mission Spacecraft Separation 44 Min 17 sec 383.39 9804.0 Fourth Stage Burn Out 43 Min 40sec 342.51 9833.5 Fourth stage Ignition 33 Min 271.32 7642.0 Third Stage Separation 9 Min 44 sec 194.87 7730.9 Third stage Ignition 4 Min 26 sec 132.53 5378.94 Second Stage Separation 4 Min 25 sec 132.31 5370.33 Heat Shield Separation 3 Min 22 sec 113.17 3624.69 Second Stage ignition 1 Min 53 sec 57.85 2387.16 First Stage Separation 1 Min 53 sec 58.00 2388.0 Air Lit Strap-on Separation 1 Min 32 sec 39.70 2024.3 Ground Lit Strap-on Separation 1 Min 10 sec 23.50 34.5 Air Lit Strap-on Ignition 25 sec 2.67 612.0 Ground Lit strap-on Ignition 0.5 sec 0.02 451.9 First stage Ignition 0 sec 0.02 451.9
The Journey As the Mars Orbiter spacecraft circles the earth, by firing the spacecraft s Liquid Apogee Motor (LAM) in six steps, the apogee of the orbit will be raised further and further. Ultimately, the spacecraft will be put on a course for arriving at Mars in September 2014. In this fuel efficient Mars Transfer Trajectory, the spacecraft travels for about 300 days under the influence of the Sun and approaches Mars. At that time, the spacecraft s speed is reduced by suitably firing its LAM to enable it to be captured into an orbit by Martian gravity. After achieving this elliptical orbit around Mars with a periareion (nearest point to Mars) of 366 km and an apoareion (farthest point to Mars) of 80,000 km, the spacecraft is scheduled to begin its six month observation of that planet and its atmosphere. The Spacecraft The 1340 kg Mars Orbiter spacecraft is based on the modified version of ISRO s well proven one ton class platform (I1K satellite bus). The spacecraft structure is built mainly by the use of lightweight Aluminium alloy and composites like Carbon Fibre Reinforced Plastic (CFRP). To keep the spacecraft within safe temperature limits, a variety of materials including Multilayer Insulation (MLI) blanket are used. The Mechanisms subsystem of the spacecraft facilitates the deployment of the spacecraft s solar panels and the high gain antenna, as well as the rotation of the solar array drive to track the sun and generate optimum electric power. The spacecraft s single solar array consisting of three panels can generate about 840 W of electric power in the Martian orbit. A 36 Ampere-Hour Lithium-Ion battery supplies power to the spacecraft during eclipse and peak power requirement periods. The transmission of spacecraft health related information to Earth, enabling the knowledge of its position in space, and the reception of telecommands from Earth are performed by the Telemetry, Tracking and Command (TTC) subsystem of the spacecraft working in S-band. The images and other science data gathered by the spacecraft s five payloads are transmitted to Earth by its 2.2 m dish shaped S-band high gain antenna. Mars Orbiter spacecraft carries a host of Sun and Star Sensors as well as an Inertial Reference Unit and accelerometers that provide information on the spacecraft s precise orientation and velocity. The microprocessor based Attitude and Orbit Control Electronics (AOCE) of the spacecraft maintains and controls the orientation and orbit of the spacecraft using its reaction wheels, thrusters and the Liquid Apogee Motor (LAM). About 850 kg of propellants required for LAM and thrusters are stored in the spacecraft s tanks.
The Payloads Mars Orbiter Mission carries five scientific payloads to observe Martian surface, atmosphere and exosphere extending up to 80,000 km for a detailed understanding of the evolution of that planet, especially the related geologic and the possible biogenic processes on that interesting planet. These payloads consist of a camera, two spectrometers, a radiometer and a photometer. Together, they have a weight of about 15 kg. Mars Colour Camera (MCC) is a versatile and multi-purpose snap shot CCD camera to map various morphological features on the Martian surface and return colour visual images of Mars and its environs. MCC is expected to observe and help us understand events like dust storms, dust devils, etc., that are known to occur on Mars. MCC will have a resolution of 19.5 m when it is at nearest point to Mars in its elliptical orbit (periareion) and will be capable of imaging the full disc of Mars starting from 63,000 km and extending upto the farthest point (apoaerion). Besides, there can be a few opportunity based objectives like imaging one of the moons of Mars Phobos and other celestial objects like comets or asteroids, if appropriately illuminated. Thermal Infra-Red Imaging Spectrometer (TIS) is a grating based spectrometer that will measure the thermal emission from Martian surface. The data acquired will be useful for mapping the temperature of the Martian surface and to study the composition and mineralogy of Mars. TIS operates in the Thermal Infrared (TIR) region (7 micron to 13 micron) and has a resolution of 258 m at periareion (around 366 km) and 55 km at apoareion (around 80,000 km). Methane Sensor for Mars (MSM) is a differential radiometer operating in the Short Wave Infrared (SWIR) region. It measures solar radiance in two SWIR channels. MSM can measure Methane concentration in the Martian atmosphere accurately. Variation of methane over different places and at different times derived from MSM data may provide some insight regarding its origin as to whether it is biological or geological. Mars Exospheric Neutral Composition Analyser (MENCA) is a quadrupole mass spectrometer based scientific payload. MENCA will be capable of measuring relative abundances of neutral constituents in the mass range of 1 to 300 atomic mass units (amu), with a unit mass resolution. It will study the neutral composition and density distribution of the Martian exosphere from about 370 km altitude and beyond. This would help in understanding the escape of the Martian atmosphere.
Lyman Alpha Photometer (LAP) is a far-ultraviolet (FUV) scientific instrument. LAP is primarily dedicated to measure the relative abundance of Deuterium and Hydrogen from their Lyman-alpha emissions in the Martian exosphere. Currently, it is aimed at the in-situ estimation of deuterium enrichment and to further the understanding of loss process of water from Martian atmosphere. Payload Primary Objective Developed by Operating range Resolution Power Require ment (W) Weight (Kg) Mars Colour Camera (MCC) Optical imaging SAC 0.4 0.7 µm R-G-B 19.5 m @ periareion 3 1.27 Thermal Infrared Imaging Spectrometer (TIS) Map surface composition and mineralogy SAC 7 13 µm 12 bands 258 m (~366km) @ periareion 55 km @ apoareion(~89000km) <6.3 3.2 Methane Sensor for Mars (MSM) Detection of Methane presence SAC 1640 1660 nm 258 m @ periareion 7.5 2.94 Mars Enospheric Neutral Composition Analyser (MENCA) Study of the neutral composition of Martian upper atmosphere SPL, VSSC 1 300 Amu 1 amu 29 normal mode 45 (Degas mode) 3.56 Lyman Alpha Photometer (LAP) Study of Escape processes of Martian upper atmosphere through Deuterium/Hydr ogen LEOS 3000 km periareion 3000km 8 1.97 SAC Space Application Centre, Ahmedabad SPL Space Physics Laboratory, Thiruvananthapuram VSSC Vikram Sarabhai Space Centre, Thiruvananthapuram LEOS Laboratory for Electro-Optic Systems, Bangalore amu Atomic Mass Unit µm micrometre nm nanometre
The Ground Segment The Ground Segment of Mars Orbiter Mission mainly consists of facilities to monitor the spacecraft and its flight status during various phases of mission, and to control them. Indian Space Science Data Centre, which processes and archives data from the spacecraft, also forms an important part of the ground segment. Besides the ground stations of ISRO Telemetry, Tracking and Command Network (ISTRAC) in India and abroad, two shipborne S-band terminals will be used to monitor the performance and flight of PSLV-C25 vehicle and Mars Orbiter Mission spacecraft over the Pacific. During the earth orbiting phase of the spacecraft, ISTRAC network of ground stations will be used. Once the spacecraft enters deep space (beyond 100,000 from the Earth), 18 and 32 metre antennas of Indian Deep Space Network (IDSN) at Byalalu near Bangalore and antennas of NASA s Deep Space Network will be utilised to communicate with the spacecraft as well as to track and control it. These two networks continue their support till the mission completion. The Spacecraft Control Centre at Bangalore acts as the nerve centre of mission operations during various phases of the mission. Publication and Public Relations Unit, ISRO November 2, 2013