GK (Astronomy)

A transponder on a satellite performs both reception and transmission of signals. It receives signals from Earth (uplink), amplifies them, shifts their frequency, and retransmits them back to Earth (downlink). This two-way communication capability is essential for satellite operations like telecommunications, broadcasting, and data relay.

INSAT (Indian National Satellite System) is a series of multipurpose geostationary satellites launched by ISRO. Among their key applications are weather forecasting, meteorological imaging, and cyclone monitoring. INSAT satellites carry dedicated instruments for weather observation and data collection.

Mercury is the closest planet to the Sun in our solar system, with an average distance of about 58 million kilometers (36 million miles). Being nearest to the Sun, Mercury has the shortest orbital period of approximately 88 Earth days and experiences extreme temperature variations.

Halley's Comet is a short-period comet visible from Earth every 75-76 years. Its average orbital period is approximately 76 years, though it can vary between 74-79 years due to gravitational perturbations from planets. The comet's last appearance was in 1986 and it will return in 2061.

Perigee is the point in a satellite's orbit where it is closest to Earth. The opposite term is apogee (farthest point). These terms are fundamental in orbital mechanics and satellite communication planning, as the varying Earth-satellite distance affects signal strength and coverage.

A light year is a unit of distance used in astronomy to measure vast distances between stars and galaxies. It represents the distance light travels in one year (about 9.46 trillion kilometers or 5.88 trillion miles). This unit is impractical for Earth-bound distances due to its enormous scale.

The Sun is a star - specifically a G-type main-sequence star (yellow dwarf) located at the center of our solar system. It generates energy through nuclear fusion in its core, converting hydrogen into helium. This distinguishes it from planets like Earth and moons like our Moon, which reflect light rather than produce it.

The photosphere is the visible surface layer of the Sun where sunlight is emitted into space. It's approximately 300-500 km thick and consists of hot plasma at about 5,500°C. Jupiter, Saturn, and the Moon have different surface structures and terminology.

ISRO (Indian Space Research Organisation) is India's national space agency, headquartered in Bengaluru. NASA is the American space agency. ISA and ISARS are not real space agencies.

Sriharikota, a spindle-shaped island on India's east coast in Andhra Pradesh, houses the Satish Dhawan Space Centre (SDSC). This is India's primary satellite launching station from where all satellite launch vehicles are fired.

Aryabhatta, India's first satellite, was launched on April 19, 1975 by the Soviet Union from Kapustin Yar using a Kosmos-3M launch vehicle. It was named after the ancient Indian mathematician-astronomer Aryabhata.

The zodiac consists of 12 signs spanning 30 degrees each along the ecliptic path: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, and Pisces.

Rakesh Sharma became the first Indian citizen to travel to space in 1984 as part of the Soviet Interkosmos program. Kalpana Chawla and Sunita Williams were Indian-born but flew as American citizens later.

A galaxy is a gravitationally bound system of stars, gas, dust, and dark matter. Our Milky Way contains 100-400 billion stars. Asteroids and meteorites are rocky bodies, while planetoids are small planets.

Venus is known as both the morning star and evening star because it orbits closer to the Sun than Earth, making it visible shortly before sunrise in the east and shortly after sunset in the west. Mercury does this too but is much fainter.

Rakesh Sharma flew aboard Soyuz T-11 to the Salyut 7 space station in April 1984, spending 7 days 21 hours 50 minutes in space. He conducted Earth observation and biotechnology experiments.

One light year equals approximately 9.46 trillion km (9.46 × 10^12 km), which is the distance light travels in vacuum in one year at 299,792 km/s. A parsec is about 3.26 light years.

RH-75 was indeed India's first sounding rocket, launched from Thumba in 1967. It marked the beginning of India's space exploration program and was a crucial milestone in developing indigenous rocket technology. The other options incorrectly attribute this achievement to Pakistan, China, and Japan.

The Pole Star (Polaris) appears stationary from Earth's perspective because it lies almost exactly above Earth's rotational axis (north celestial pole). While other stars appear to move across the sky due to Earth's rotation, Polaris remains fixed in the same position, making it useful for navigation.

The Great Bear constellation (Ursa Major) is most prominently visible in the night sky during April in the Northern Hemisphere. During spring months, this constellation appears high in the sky and is easily recognizable, making April the best time for observation.