Context:
Aditya-L1 mission has recently reported its first science result.
- The Visible Emission Line Coronagraph (VELC) onboard Aditya-L1 precisely estimated the onset time of a coronal mass ejection (CME) that erupted on the Sun.
Aditya – L1:
- 1st space-based Indian observatory to study the Sun.
- Spacecraft – Planned to be placed in a halo orbit around the Lagrangian point 1 (L1) of the Sun-Earth system.
- Launch vehicle: PSLV C57
- Scientific objectives:
- Study of Solar upper atmospheric (chromosphere and corona) dynamics.
- Study of chromospheric and coronal heating, physics of the partially ionized plasma, initiation of the coronal mass ejections (CMEs), and solar flares.
- Observe the in-situ particle and plasma environment.
- Study drivers for space weather (origin, composition and dynamics of solar wind).
- 7 payloads:
- Visible Emission Line Coronograph (VELC)
- Solar Ultraviolet Imaging Telescope (SUIT)
- Solar Low Energy X-ray Spectrometer (SoLEXS)
- High Energy L1 Orbiting Xray Spectrometer (HEL1OS)
- Aditya Solar Wind Particle Experiment (ASPEX)
- Advanced Tri-axial High Resolution Digital Magnetometers
Mission Uniqueness:
- 1st time spatially resolved solar disk in the near UV band.
- CME dynamics close to the solar disk to provide information consistently.
- On-board intelligence to detect CMEs and solar flares.
- Directional and energy anisotropy of solar wind using multi-direction observations.
What are halo orbits?
- These are periodic and three-dimensional orbits resulting from an interaction between the gravitational pull of the two planetary bodies and centrifugal force on a spacecraft.
- Halo orbits exist in any 3-body system. E.g., Earth-Moon orbiting satellite system.
- Mainly linked to L1, L2 or L3.
- Benefits of placing Aditya-L1 in Halo Orbit:
- Ensuring a mission lifetime of 5 years
- Reducing fuel consumption (minimising station-keeping manoeuvres)
- Ensuring an unobstructed view of the sun
Facts on other Missions to the Sun:
- NASA’s Parker Solar Probe (part of NASA’s ‘Living with a Star’ programme) – To track the movement of energy and heat through the Sun’s corona and investigate the origin of the acceleration of the solar wind.
- Other active spacecraft monitoring the Sun include SOHO (Solar and Heliospheric Observatory) – European Space Agency, ACE, IRIS, WIND, Hinode, the Solar Dynamics Observatory, STEREO, Kuafu-1 solar probe (China) etc.
- SOHO mission (longest-lived Sun-watching satellite to date) is placed near L1 point while NASA’s James Webb Space Telescope is placed around L2 point.
Structure of Sun:
- Photosphere: Innermost layer of the Sun’s atmosphere, visible to the naked eye. Temperature ranges from 6500K to 4000K.
- Chromosphere: Layer above the photosphere. Temperature ranges from 4000K to 8000K.
- Transition Region: Thin layer between the chromosphere and corona. Temperature rapidly increases from 8000K to 500,000K.
- Corona: Outermost layer of the Sun’s atmosphere. Extends millions of kilometers into space. Temperature can reach millions of degrees Kelvin. Visible during a total solar eclipse or using a coronagraph.
- Solar Flares: Intense bursts of radiation and particles from the Sun’s surface. Often associated with Coronal Mass Ejections (CMEs). Can disrupt satellite communications, power grids, and pose risks to astronauts.
- Sunspots: Dark, cooler regions on the Sun’s surface caused by intense magnetic activity.
- Coronal Holes: Dark areas in the solar corona, cooler and less dense than the surrounding plasma. Regions of open magnetic field lines. More common during solar minimum.
- Solar Prominences: Large, bright, arch-shaped structures of plasma extending from the Sun’s surface into the corona.
- Solar Wind: Continuous stream of charged particles (mostly protons and electrons) emitted by the Sun.
- Picoflare Jets: Small, intermittent eruptions of plasma from coronal holes.
Source: TH
Previous Year Question
Which of the following pair(s) is/are correctly matched?
Spacecraft: Purpose
1. Cassini-Huygens: Orbiting the Venus and transmitting data to the Earth
2. Messenger: Mapping and investigating the Mercury
3. Voyager 1 & 2: Exploring the outer solar system
Select the correct answer using the codes given below.
[UPSC Civil Services Exam – 2014 Prelims]
(a) 1 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
Answer: (b)
Explanation:
Cassini-Huygens was the fourth space probe to visit Saturn.