With reference to 'Astrosat', the astronomical observatory launched by India, which of the following statements is/are correct? 1. Other than USA and Russia, India is the only country to have launched a similar observatory into space. 2. Astrosat is a 2000 kg satellite placed in an orbit at 1650 km above the surface of the Earth. Select the correct answer using the code given below.

Explicitly identifies AstroSat as an ISRO mission that makes scientific observations of stars and celestial objects (i.e., a space-based astronomical observatory).

Use this definition to look for other countries/agencies described elsewhere in the snippets as having comparable space science capabilities and infer they could/likely have launched space telescopes.

States India became the fourth agency to reach Mars orbit after the Russian, American, and the European space agencies, highlighting that those agencies have advanced interplanetary and space-science capabilities.

A student can reasonably check that agencies with such deep space capability (Russia/US/Europe) have also launched space observatories (e.g., by consulting a world map of space agencies or lists of major telescopes).

Shows the USA is the major player in space with substantially larger spending than India, implying broad capabilities in space science missions.

Combine this spending/capability clue with knowledge of US space history to infer the US has launched many space observatories and thus is a likely answer to the question.

Describes Mangalyaan as carrying scientific instruments to study Mars, illustrating a pattern: countries that conduct planetary science missions also field space science payloads.

From this pattern, a student can extend that other countries conducting planetary/space science (e.g., those mentioned in [2]) are likely to have launched space telescopes too, and then verify with basic external references.

Identifies AstroSat as an ISRO scientific observatory satellite (used for observations of stars and celestial objects), placing it in the class of dedicated scientific/astronomy satellites.

A student could compare typical masses of similar space-observatory satellites (from launch manifestues or a world map of launch providers) to form a plausible mass range for AstroSat.

Describes categories of Indian satellites (INSAT, IRS) and the role of satellites in India, giving context that India operates multiple satellite types with differing sizes and purposes.

One could use the satellite category and mission type (astronomy/science vs Earth observation/communication) to narrow expected mass ranges from known examples in each category.

Notes India has developed a variety of satellites since early programmes, implying a historical range of satellite sizes and launch vehicles used by ISRO.

By consulting known ISRO launch vehicle payload capacities and past satellite masses (e.g., Aryabhatt, Rohini), a student could judge if AstroSat's mass fits within typical payload limits.

Explains the scientific definition and units of mass (grams, kilograms) and how mass is measured, ensuring clarity on what 'mass in kilograms' means.

A student could use this to convert any reported mass in grams or other units into kilograms for direct comparison to the question.

Reinforces the distinction between mass and weight and that mass units are kg, helping avoid confusion when reading satellite specifications that sometimes mix terms.

Use this to interpret technical spec sheets correctly (mass in kg vs weight in N) when checking external sources for AstroSat's mass.

Gives a general rule: most artificial satellites orbit about 800 km above Earth's surface and have ~100 minute orbital periods.

A student could use this as a benchmark for 'typical' low Earth orbits and compare any claimed altitude for Astrosat to the ~800 km typical value to see if it is plausible.

Defines the exosphere (700–1000 km) as where many mid- and high-earth-orbit satellites reside because atmospheric drag is minimal.

One could place a claimed Astrosat altitude within or outside this 700–1000 km band to infer whether it is consistent with being in the exosphere (less drag) versus lower layers.

States that above ~480 km the atmosphere is rarified and is called the exosphere, implying a practical cutoff for where satellites experience very low drag.

Use this ~480 km threshold to judge whether a given altitude for Astrosat would be in a low-but-not-exosphere regime (<480 km) or in the rarified region (>480 km).

Places the ionosphere between about 80 and 400 km, giving another reference band for where many satellites are not (i.e., above ionosphere implies higher orbits).

A student can check if a claimed Astrosat altitude lies below, within, or above the ionosphere (80–400 km) to assess whether it matches typical ionospheric or higher-altitude satellite regimes.