Of all the planets in the solar system, Mars has sparked the greatest human interest. The conditions in Mars are believed to be hospitable since the planet is similar to Earth in many ways. For ages, humans have been speculating about life on Mars. However, the question that is to be still answered is whether Mars has a biosphere or ever had an environment in which life could have evolved and sustained.
The Mars Orbiter Mission (MOM) also called Mangalyaan is a Mars orbiter launched by the Indian Space Research Organization (ISRO). It was launched on the 5th of November 2013 into the space. The main objectives of the first Indian mission to Mars is to develop the technologies required for design, planning, management and operations of an interplanetary mission.
Following are the major objectives of the mission:
A. Technological Objectives:
- Design and realization of a Mars orbiter with a capability to survive and perform Earth bound manoeuvres, cruise phase of 300 days, Mars orbit insertion / capture, and on-orbit phase around Mars.
- Deep space communication, navigation, mission planning and management.
- Incorporate autonomous features to handle contingency situations.
B. Scientific Objectives:
- Exploration of Mars surface features, morphology, mineralogy and Martian atmosphere by indigenous scientific instruments.
The spacecraft is being currently monitored from the Spacecraft Control Centre at ISRO Telemetry, Tracking and Command Network (ISTRAC) in Bangalore with support from Indian Deep Space Network (IDSN) antennae at Byalalu.
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.
Lyman Alpha Photometer (LAP) Lyman Alpha Photometer (LAP) is an absorption cell photometer. It measures the relative abundance of deuterium and hydrogen from lyman-alpha emission in the Martian upper atmosphere (typically Exosphere and exobase). Measurement of D/H (Deuterium to Hydrogen abundance Ratio) allows us to understand especially the loss process of water from the planet.
Methane Sensor for Mars (MSM)
MSM is designed to measure Methane (CH4) in the Martian atmosphere with PPB accuracy and map its sources. Data is acquired only over illuminated scene as the sensor measures reflected solar radiation. Methane concentration in the Martian atmosphere undergoes spatial and temporal variations.
Mars Exospheric Neutral Composition Analyser (MENCA)
MENCA is a quadruple mass spectrometer capable of analyzing the neutral composition in the range of 1 to 300 amu with unit mass resolution. The heritage of this payload is from Chandraâ€™s Altitudinal Composition Explorer (CHACE) payload. MENCA is a quadrupole mass spectrometer based scientific payload, capable of measuring relative abundances of neutral constituents in the mass range of 1 to 300 amu, with a unit mass resolution.
Mars Color Camera (MCC)
This tri-color Mars color camera gives images & information about the surface features and composition of Martian surface. They are useful to monitor the dynamic events and weather of Mars. MCC will also be used for probing the two satellites of Mars-Phobos & Deimos. It also provides the context information for other science payloads.
Thermal Infrared Imaging Spectrometer (TIS)
TIS measure the thermal emission and can be operated during both day and night. Temperature and emissivity are the two basic physical parameters estimated from thermal emission measurement. Many minerals and soil types have characteristic spectra in TIR region. TIS can map surface composition and mineralogy of Mars.
The orbiter need to face many challenges up there in space. The major challenges are as follows:
The bus needs to cope with a wide range of thermal environment, from Near Earth conditions with Sun and Earth contributions (hot case) to Mars conditions where eventually eclipses and reduced solar flux give rise to cold case issues.
The average solar flux at Mars orbit is 589 W/Sq.m, or about 42% of what is experienced by an Earth-orbiting spacecraft. As a result of the eccentricity of Mars orbit, however, the solar flux at Mars varies by +/- 19% over the Martian year, which is considerably more than the 3.5% variation at Earth.
The main frame bus elements and payloads are basically designed for interplanetary missions capable of operating in Earth Burn Manoeuvres (EBN), Mars Transfer Trajectory (MTT) and Martian Orbit (MO) environments. The bus unit components are selected with respect to a cumulated dose of 6 krads below 22 AWG aluminium shielding. Parts have been considered as directly suitable, if they have been evaluated successfully up to 12 krads (margin factor of 2).
The communication systems for the Mars mission are responsible for the challenging task of communication management up to a distance of 400 million km. It consists of Telemetry, Tracking and Commanding (TTC) systems and Data transmission systems in S-band and a Delta Differential One-way Ranging (Delta-DOR) Transmitter for ranging.
The TTC system comprises of coherent TTC Transponders, TWTAs (Travelling Wave Tube Amplifiers), a near omni coverage antenna system, a High Gain Antenna system, Medium Gain Antenna and corresponding feed networks.
The High Gain Antenna system is based on a single 2.2 meter reflector illuminated by a feed at S-band.
One of the major challenges in the design of power system is due to the larger distance of the satellite from the Sun. The power generation in Mars orbit is reduced to nearly 50% to 35% compared to Earth’s orbit.
The power bus configuration comprises of a single wing of solar array with 7.56 m2 area generating about 840 W during sunlit and normal incidence in Martian orbit, and a 36 Ampere-Hour Lithium-Ion battery supports the power load during launch phase, initial attitude acquisition, eclipse, Earth burns, MOI, safe mode and data transmission phases.
Proplusion System consists of one 440N Liquid Engine and 8 numbers of 22N thrusters. The propellant tanks have combined storage capacity up to 852 kg propellant. The 22N thrusters are used for attitude control during the various activities of the mission like, orbit raising using liquid engine, attitude maintenance, Martian orbit maintenance (if any) and momentum dumping.
As the critical operation of Martian Orbit Insertion with Liquid Engine burn occurs after 10 months of launch, suitable isolation techniques are adopted to prevent fuel/ oxidiser migration issues.
Given that the Round-trip Light Time (RLT) from Earth to Mars can vary anywhere between 6 to 43 minutes, it would be impractical to micromanage a mission from Earth. Due to this communications delay, mission support personnel on Earth cannot easily monitor and control all the spacecraft systems in real-time basis. Therefore, the configuration includes the use of on-board autonomy to automatically manage both the nominal and non-nominal scenarios on-board the spacecraft.
Trans Mars Injection (TMI), carried out on Dec 01, 2013 at 00:49 hrs (IST) has moved the spacecraft in the Mars Transfer Trajectory (MTT). With TMI the Earth orbiting phase of the spacecraft ended and the spacecraft is now on a course to encounter Mars after a journey of about 10 months around the Sun
- The Polar Satellite Launch Vehicle, PSLV-C25, injected the Spacecraft into an Elliptical Parking Orbit with a perigee of 250 km and an apogee of 23,550 km.
- Further, six orbit raising manoeuvers gradually raised the apogee of the spacecraft to 1,92,874 km, using the 440 N Liquid Engine on board.
- The last manoeuver, termed as Trans Mars Injection (TMI), moved the spacecraft in the Mars Transfer Trajectory (MTT). Spacecraft crosses Earth’s Sphere of Influence (SOI) and enters heliocentric elliptic cruise phase.
- A series of Trajectory Correction Manoeuvres (TCMs) are planned in cruise phase, using Attitude and Orbit Control System (AOCS) thrusters to achieve desired Mars arrival conditions.
- At the end of the heliocentric phase, Mars Orbit Insertion (MOI) manoeuvre will be carried out by firing the Liquid Engine onboard and the spacecraft will be inserted into the intended Martian Orbit.
- The spacecraft will focus on in-depth study of morphology of the Martian surface and probe the composition of its atmosphere and the space environment.