science

IRS-1D

IRS-1D is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand IRS-1D rather than just read about it. In short: IRS-1D is the seventh satellite in Indian Remote Sensing satellite series of Earth Observation satellites, built, launched and maintained by Indian Space Research Organisation (ISRO). The satellite has similar capabilities as that of ISRO's IRS-1C satellite with some improvements added for better imagery particularly in thematic mapping.

Key takeaways

IRS-1D belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect IRS-1D to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of IRS-1D from memory before moving on to harder problems.

Reference excerpt

IRS-1D is the seventh satellite in Indian Remote Sensing satellite series of Earth Observation satellites, built, launched and maintained by Indian Space Research Organisation (ISRO). The satellite has similar capabilities as that of ISRO's IRS-1C satellite with some improvements added for better imagery particularly in thematic mapping.

Launch The 1250 kg IRS-1D is an Indian remote sensing Sun-synchronous orbiter that was launched by the PSLV-C1 (Polar Satellite Launch Vehicle) launch vehicle from Sriharikota (in southeast India) at 04:47 UTC. The 44.4 metres, four-stage, 494-ton PSLV-1C is now an operational vehicle, after earlier test launches, it is the fourth launch vehicle PSLV. Orbit maneuvers may be planned to raise the perigee. Due to a slight under performance of PSLV fourth stage, IRS-1D was injected with a velocity that was 130 m/sec less than the required 7446 m/sec. This minor shortfall in the injection velocity resulted in IRS-1D being injected into a polar orbit with an apogee of 822 km and a perigee of 301 km instead of the intended 817 km circular orbit. But, ISRO scientists, monitoring and controlling the satellite from ISRO Telemetry, Tracking and Command Network (ISTRAC) executed meticulously planned orbit manoeuvres to successfully put IRS-1D into a functional Sun-synchronous orbit of 740 km perigee and 817 km apogee.

Instruments The satellite carried following instruments on board:

Linear Imaging Self-Scanning Sensor-3 (LISS-3) of 23.5 m (77 ft) resolution in (VIS / NIR, 70.5 m (231 ft) resolution in short-wave infrared (SWIR), for high-resolution land and vegetation observation Panchromatic Camera (PAN) of 5.8 m (19 ft) resolution, for very-high-resolution land imagery Wide-Field Sensor (WiFS) of 190 m (620 ft) resolution, for land and vegetation observation An on board tape recorder stores data over unreachable intervals. Sensed data on Indian and foreign terrains will be sold through an American company (after the usual clearance by Indian military).

Mission IRS-1D completed its services on 15 January 2010 after serving for 12 years.

Worked examples

Example 1 — a first encounter with IRS-1D

Start with the simplest possible case. Write down what IRS-1D claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to IRS-1D before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about IRS-1D ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of IRS-1D

In research: IRS-1D appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses IRS-1D in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: IRS-1D is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1997 in India, Earth observation satellites of India, Satellite launch anomalies, so understanding it makes those chapters shorter.
In everyday life: Look for IRS-1D outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study IRS-1D in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what IRS-1D means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain IRS-1D out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is IRS-1D in simple terms?

Why does IRS-1D matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study IRS-1D?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on IRS-1D.