Theory:

     Meanwhile Comet Dutta was following its predicted path. In due course it developed its tail. It circled round the Sun without breaking apart; nor did it evaporate. The scientists on Project Light Brigade therefore knew that the threat of collision was now very much real.
 
     In the middle of October, Duttada got a letter from Sir John. In the midst of descriptions of the meeting of the Royal Astronomical Society, the unseasonably warm weather, the opening matches of the football season and a recent bye-election, Duttada spotted the sentence he was eagerly looking for: “The charge of the Light Brigade has begun. Let us hope for the best.” So the spacecraft had been launched on time.
 
     But will it achieve the rendezvous in time and at the right place? Will the remote control detonation work? What if the gigantic nuclear pile fails to fire?
Explanation:
 
Meanwhile, as Comet Dutta circled the Sun, it began to grow its tail, as expected. This is because, as a comet approaches the sun, the heat forces its gases to evaporate, releasing dust and microparticles. The movement of these components, which form a tail, is influenced by the sun's radiation pressure.
 
A comet can sometimes disintegrate altogether. Comet Dutta did not vanish because it was less likely to evaporate as it approached the sun. Furthermore, no natural disasters destroyed Comet Dutta. As a result, Project Light Brigade scientists realised that the chance of a collision had significantly increased. And, if the international conference's decision to halt Comet Dutta from attacking the Earth was not followed, Comet Dutta was set to hit the Earth on December 15.
 
Duttada got a letter from Sir John in the middle of October. In the middle of reports on the Royal Astronomical Society's annual conference, the unexpectedly warm weather, the opening matches of the football season, and a recent bye-election, Duttada's much awaited message was also mentioned by Sir John that the Light Brigade's charge had begun. As a result, it's been assumed that the operation against Comet Dutta has begun. The spacecraft was launched on schedule by scientists (October 9). They were also expecting that Comet Dutta's nuclear explosion would be deflected by the launched spacecraft.
 
Though it was mentioned that the spacecraft was launched, Duttada was sceptical about whether the spacecraft would arrive on time and at the correct location to meet Comet Dutta. Is it possible to detonate a bomb with a remote control? What happens if the gigantic nuclear pile doesn't go off? After reading the letter, Duttada was disturbed by a slew of questions.
 
Meaning of difficult words:
  
S.No
Words
Meaning
1.
ThreatA possibility of danger or harm
2.
Charge A violent attack
3.
Rendezvous  A meeting place
4.
Detonation An act of making an explosive device to explode
Reference:
National Council of Educational Research and Training (2008). The Comet - II — JAYANT NARLIKAR (pp. 81-87). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.