Polar Sundial at VSSC: A Marvel of Science and Precision

Sub: Sci

Sec: Space sector

Why in News

The Vikram Sarabhai Space Centre (VSSC) has unveiled a polar sundial with analemmatic correction at its Space Museum in Thumba, Kerala. This unique sundial accurately provides Indian Standard Time (IST) and the date, making it a significant addition to India’s space science initiatives.

Polar Sundial:

Unlike conventional sundials, the VSSC polar sundial uses analemmatic correction to provide IST along with the date.
Conventional sundials only show local solar time, which can differ from standard clock time.
The sundial incorporates inverted analemma curves instead of straight hour lines, allowing it to automatically convert local solar time to mean solar time.
The sundial is configured based on the latitude of Thumba, ensuring precise alignment with the true north-south direction.
The sundial plate is parallel to the Earth’s polar axis, while the style (shadow-casting element) is aligned with the Earth’s equatorial plane.
The style of the sundial is a 1.6 ft tall, 3D-printed replica of the Rohini series RH200 sounding rocket, symbolizing ISRO’s contributions to space exploration.
The sundial was developed by VSSC’s Space Physics Laboratory, Technology Transfer and Documentation Group, and Construction Management Group.
Officially installed in November 2024 in the Rocket Garden of VSSC’s Space Museum.

Analemmatic Correction:

The sundial incorporates analemma curves, accounting for the Earth’s tilt and elliptical orbit.
This ensures year-round accuracy by converting local solar time to mean solar time.
An additional longitude correction is applied to align with IST, based on Thumba’s geographical location.

Indian Standard Time (IST):

IST is the time observed across India and Sri Lanka, set at GMT+5:30.
Based on the 5° East longitude passing near Mirzapur, Uttar Pradesh.
Ensures a single time zone for the entire country despite its longitudinal span.
Introduced in 1906 during British rule to unify timekeeping in India.
IST is 5 hours and 30 minutes ahead of Coordinated Universal Time (UTC).

Vikram Sarabhai Space Centre (VSSC):

Founded in 1963; named after Vikram Sarabhai, the father of the Indian space program.
Situated in Thumba, Kerala, near the Arabian Sea coast.
ISRO’s lead centre for the development of launch vehicle technology.
Major Contributions:
- Development of Polar Satellite Launch Vehicle (PSLV) and Geosynchronous Satellite Launch Vehicle (GSLV).
- Creation of sounding rockets like the Rohini series.

Thumba:

A coastal village in Thiruvananthapuram, Kerala.
Known for the Thumba Equatorial Rocket Launching Station (TERLS), established in
Geographical Advantage:
- Close to the Earth’s magnetic equator, ideal for studying atmospheric and ionospheric conditions.
- Enables efficient rocket launches for scientific experiments.
Previously housed the Mary Magdalene Church, converted into ISRO’s space museum.
Site of India’s first rocket launch (Nike-Apache) in 1963.