Aditya L1 Mission

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:

• 1^st 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)
  • Plasma Analyser Package for Aditya (PAPA)
  • Advanced Tri-axial High Resolution Digital Magnetometers

Mission Uniqueness:

• 1^st 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.

---