Jupiter is descending

Jupiter is descending
 

http://www.gutenberg.org/files/2346/2346-h/2346-h.htm "Suppose that I were Brooks or Woodhouse, or any of the fifty men who have good reason for taking my life, how long could I survive against my own pursuit? A summons, a bogus appointment, and all would be over.
...

Again and again his word has decided the national policy. He lives in it. He thinks of nothing else save when, as an intellectual exercise, he unbends if I call upon him and ask him to advise me on one of my little problems. But Jupiter is descending to-day. What on earth can it mean? Who is Cadogan West, and what is he to Mycroft?"
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1. Holmes is assuming he were pursuing himself; does the SUMMONS line mean if so, he would need only summon himself to catch himself because he would turn himself in to authority(or authorities?)?

2. Does the JUPITER part mean the person, his brother, is doing things inferior, which does not comply with his usual way of being lofty and unreachable?

This means it would be trivial for him to set up an ambush to take his life.

This means that his brother Mycroft is very important, and normally doesn't bother with Holmes' unimportant problems, but that today he is coming to visit.

Thank you~

But for TRIVIAL, do you mean taking his own life is easy?