Space Science & Exploration

* Satellite navigation is based on the use of range measurements between navigational satellites and the user. Information about the satellite's coordinates is given to the user through a navigation signal. Range measurements are based on the calculation of the receiving signal time delay compared with the signals generated by the user equipment. * Currently, there are four global systems viz., GPS from the USA, GLONASS from Russia, Galileo from the European Union, and BeiDou from China. In addition, there are two regional systems viz., NavIC from India and QZSS from Japan. * Global navigation system caters to the users in the entire world, whereas the regional navigation system caters to the users in the limited service area. Hence, option (D) is the correct answer.

Out of the listed effects of a major solar storm, the most likely ones are Statement 1 is correct. A solar storm can disrupt the Earth's ionosphere, which can affect the signal transmission of GPS and other radio-based navigation systems. Statement 3 is correct. Strong currents induced by the solar storm in power grids can damage transformers and cause widespread blackouts. Statement 4 is correct. Solar storms can energize particles in the Earth's magnetosphere, leading to spectacular auroras at lower latitudes than usual. Statement 6 is correct. The drag from a solar storm can alter the orbits of satellites, especially those in lower Earth orbit. Statement 7 is correct. Similar to GPS, radio communication can be affected by disturbances in the ionosphere. Statement 2 is incorrect. Tsunamis are caused by underwater earthquakes or volcanic eruptions, not solar storms. Statement 5 is incorrect. While a solar storm could potentially ignite some fires through electrical sparks, this is not a widespread effect. Therefore, codes 2 and 5 should not form the part of answer.

It is a delivery system that uses a low Earth orbit to bypass early warning systems and deliver warheads on targets very quickly. FOBS launches a warhead into a low Earth orbit trajectory instead of a full ballistic missile arc. These systems are typically designed to detect missiles launched on high ballistic trajectories. A FOBS warhead in a low orbit might be harder to detect until it re-enters the atmosphere for its final approach to the target. Due to the orbital path, the time between re-entry and target impact can be shorter compared to a traditional ballistic missile attack.

Statement A is incorrect: The distance between stellar bodies does change, but often very slowly or in predictable orbits. Planets orbit stars, stars orbit galactic centers, and galaxies orbit each other, all causing continuous changes in distance. And this statement is not related to why distance is measured in light years. Statement B is incorrect: While the gravitational constant is fundamental, the effective gravity of stellar bodies changes due to shifts in their mass (e.g., fusion, stellar winds), changes in their radius/size (expanding into red giants, collapsing into white dwarfs/neutron stars), and changes in the distance between them as they orbit. And this statement is not related to why distance is measured in light years. Statement C is incorrect: Though mostly light travels in a straight line, it can be bent by Gravity- phenomenon known as Gravitational Lensing. Statement D is correct: the speed of light does not change in a vacuum. So, it is a constant that can be used for measurement.

The description mentions three spacecraft in an equilateral triangle formation with million-kilometre sides using lasers for measurement.
This matches the design of the Evolved Laser Interferometer Space Antenna (eLISA) mission.
eLISA is a proposed space observatory aiming to detect gravitational waves using precisely positioned spacecraft. Voyager-2 and New Horizons are single spacecraft on exploration missions, not designed for gravitational wave detection. LISA Pathfinder was a precursor mission to test technologies for eLISA, not the full mission itself. Therefore, based on the details provided, the experiment refers to the Evolved LISA mission.

Remote sensing is the process of detecting and monitoring the physical characteristics of an area by measuring its reflected and emitted radiation at a distance from the targeted area. Statement 1 is correct. Satellite images and remote sensing data can indeed be used to estimate the chlorophyll content in vegetation. This is done by measuring the reflectance of light from the vegetation. The chlorophyll in plants absorbs light for photosynthesis, and the amount of light reflected back can give an estimate of the chlorophyll content. Statement 2 is correct. Satellite images and remote sensing data can also be used to estimate greenhouse gas emissions. This is done by detecting the radiations emitted by the substances in the rice paddies. Statement 3 is correct. Satellite images and remote sensing data can be used to measure land surface temperatures as well. This is done by detecting the infrared radiation emitted by the land surface. Therefore, all three parameters can be measured or estimated using satellite images or remote sensing data.

The merger of black holes is expected to generate powerful gravitational waves. Gravitational waves are ripples in spacetime caused by accelerating massive objects. Detecting these waves with instruments like LIGO (Laser Interferometer Gravitational-Wave Observatory) allows us to study these events even when they are too far away or obscured to observe directly. This opens a new window for astronomical observations.

IRNSS is an independent regional navigation satellite system being developed by India. Statement 1 is correct: The Indian Regional Navigation Satellite System (IRNSS) indeed has three satellites in geostationary orbits and four satellites in geosynchronous orbits. Statement 2 is incorrect: It is designed to provide accurate position information service to users in India as well as the region extending up to 1500 km from its boundary, which is its primary service area. An Extended Service Area lies between primary service area and area enclosed by the rectangle from Latitude 30 deg South to 50 deg North, Longitude 30 deg East to 130 deg East. Statement 3 is incorrect: While India has been working on enhancing the coverage of its navigation system, as of the given timeframe (2019), it does not have full global coverage. The system is primarily regional, although there are plans for augmentation and expansion.

GPS, or Global Positioning System, is a satellite-based navigation system that provides geolocation and time information to a GPS receiver anywhere on or near the Earth. It has a wide range of applications. Statement 1 is correct. GPS is used in mobile phones for various purposes such as location tracking, navigation, and location-based services. Statement 2 is correct. GPS is used in banking operations for ATM location services and for time-stamping transactions, which is crucial for maintaining accurate records. Statement 3 is correct. GPS is used for time-stamping power system measurements, which is vital for grid stability and synchronization. Therefore, GPS technology can be used in all the three areas mentioned.

Statement 1 is correct: According to Einstein's General Theory of Relativity, gravity can bend light. This phenomenon is known as gravitational lensing. Statement 2 is correct: The General Theory of Relativity led to the prediction of an expanding universe, which has been confirmed by observational evidence. Statement 3 is correct: According to the General Theory of Relativity, the presence of matter and energy warps the fabric of space and time around it, which is the underlying cause of the gravitational force. So, all three statements are correct.