Which one of the following is the most important reason for the establishment of the Vikram Sarabhai Space Centre at Thumba?

The primary reason Thumba was chosen for TERLS/VSSC was its location on the geomagnetic (magnetic) equator, which produces a uniquely strong equatorial electrojet and horizontal geomagnetic field favorable for in-situ ionospheric and upper-atmosphere studies. Book evidence states TERLS was built because a strong equatorial electrojet current flowed over Thumba and that it was very close to the geomagnetic equator, making it ideal for sounding‑rocket launches for space research [1]. Official ISRO material similarly explains Thumba’s selection as a magnetic‑equatorial location where the geomagnetic field is horizontal, enabling study of distinctive plasma/ionospheric processes (Equatorial Electrojet, spread‑F, etc.) with rockets [2].

Sources

1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 5: Earths Magnetic Field (Geomagnetic Field) > Explanation: > p. 78
2. [2] https://www.vssc.gov.in/upperAtmosphericStudies.html