The ISRO 2016-2017 budget is approximately $1.1 billion USD [1]. The national budget is about $301 billion USD [2]. That means that ISRO constitutes approximately 0.37%.
Entitlements come directly out of payroll taxes, so it's not a legitimate comparison. You'd want to compare defense spending, as that is the largest spending item that comes from federal income tax receipts.
When the latter fail to cover the former, those entitlements will be paid out of income taxes.
I don't think it's honest to lump out a preferred pool of spending like that. I could similarly claim all spending linked to corporate and capital gains taxes not be counted as part of the budget.
I mean, we could argue about this all day, no (although, the income is separated logically, which is why I made my argument in parent comment; it would take Congressional effort to spend payroll tax income on non-entitlement spending)? Sure, federal tax receipts will be used to replenish social security and Medicare, but I'm fine with that. We can afford to cut defense spending back, as we spend more than the next 8 countries combined. That's our own money being squandered.
[1]: http://www.isro.gov.in/budget-glance
[2]: http://indiabudget.nic.in/glance.asp