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MATLAB : Fourier transform

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By Nuno Nogueira, CC BY-SA 2.5, https://commons.wikimedia.org/w/index.php?curid=3912826 MATLAB has been  crucial programming language across worldwide that let us express matrix and array mathematics directly. In signal processing and communication it plays vital role in analysing and exploring time series data in time domain or frequency domain. For analysing non periodic signals in frequency domain we use Fourier transform instead of Fourier series ,which is used to express periodic signals in terms of infinite sum of sinusoidal terms .   Fourier transform can exist for :      1. Energy signals      2. Power signals       3. Impulse signals  That means absolutely integrable signals can have their Fourier transform only.  Formula for Fourier transform;   Then its come to use Fourier transform in MATLAB. So here is the code for Fourier transform of sinusoidal wave , for any other signal we ...
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Chandrayaan : A glorious legacy

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In series of posts celebrating the success of ISRO, this is our third post and in this, we are going to remember a milestone of ISRO's journey, Chandrayaan-1.


                                                                                                                     pic by:- Universe today

Chandrayaan -1 was India's first mission to the moon. It was launched by ISRO in October 2008 and it was active until August 2009. The mission was a significant uplift to India's space program as most of the technologies used were developed in India. This mission is well known for the discovery of evidence of water molecules on the moon.

MISSION HISTORY & OBJECTIVE

The word  Chandrayaan means "Moon craft" in Sanskrit. Chandrayaan 1 project was announced by prime minister Atal Bihari Vajpayee in his Independence Day speech in 2003. Then it was discussed among 100 of eminent space scientists and engineers and finally, the mission was approved. This mission consists of a lunar orbiter and an impactor.

It was launched on 22nd October 2008 using a PSLV-XL rocket from Satish Dhawan Space Centre at Sriharikota, Andhra Pradesh. The orbiter was cuboid in shape with approximately 1.5 m dimensions and it was mainly powered by its solar array.

The main objectives of the mission were:

  • to design and launch a spacecraft using Indian-made launch vehicle.so, PSLV was used. To know more about PSLV read: PSLV and ASLV
  •  to measure the impact of a sub-satellite on the surface of Moon in order to plan future soft- landing missions. The impactor was used for this purpose and it performed its job successfully.
  • to map the height variations of the lunar surface.
  • mineralogical and chemical imaging of polar regions.
  • searching lunar surface for water and ice.
  • To increase scientific knowledge about Moon's origin and evolution.

MAJOR INSTRUMENTS USED

The mission consists of five Indian as well as six foreign instruments.

Indian Instruments

  • Terrain Mapping Camera: It was used to map the topography of the Moon. It worked in the visible region.
  • Hyper Spectral Imager:  It was used to perform the mineralogical mapping.
  • HEX: It was a high energy gamma x-ray spectrometer.
  • Lunar Laser Ranging Instrument: It was also used to determine the altitude of surface topography but by using infrared laser lights. 
  • Moon Impact Probe: It consists of a Radar altimeter for measurement of altitude and a spectrometer for measuring the constituents of the lunar atmosphere. It also carried a picture of Indian Flag and thus India became the fourth nation to place a flag on the Moon.

Foreign Instruments

  • Moon Mineralogy Mapper: Spectrometer to map the mineral composition of the lunar surface.
  • C1XS: X-ray fluorescence spectrometer.
  • Sub-keV Atom Reflecting Analyser, SARA, Mini-SAR and RANDOM-7.

TRAJECTORY

                                                                                                                                                 pic by:- European space agency

Chandrayaan-1 doesn't take the direct trajectory to the Moon. It was sent to the Moon in a series of orbit-increasing movements around the Earth over a period of 21 days. On 14 November 2008, the impactor separated from the orbiter and struck the south pole making all Indians proud.
The orbiter was expected to survey the lunar surface, especially polar regions for a period of two-year but it operated for only 312 days but most of the goals of the mission were achieved.

ACHIEVEMENTS

  • The impactor that hit the moon surface ejected sub-surface soil which helped in analyzing it for the presence of lunar water-ice. This mission discovers the presence of water molecules in lunar soil and the presence of ice at the polar region.
  •  This mission also helped in the detection of past tectonic activities. 
  • The presence of iron was confirmed as Moon Minerology Mapper mapped the mineral content on the lunar surface.
  • The terrain mapping camera took about 70,000 three dimensional images including the image of the landing site of Apollo 15.
After 9 months of operation, the orbiter starts suffering from technical issues including the failure of star tracker and poor thermal shielding which resulted in overheating of the orbiter. On 28 August 2009, the communication with the spacecraft was suddenly lost and ISRO declared the end of the mission. This is how a glorious chapter of ISRO's journey ended.

-By Aashi Kumari

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