It has been another busy week for Australia's top brokers. This has led to the release of a number of broker notes.

Three broker buy ratings that you might want to know more about are summarised below. Here's why brokers think these ASX shares are in the buy zone:

According to a note out of Bell Potter, its analysts have retained their buy rating on this defence and space company's shares with a trimmed price target of $2.20. The broker believes that the company's equity raise and investment in long lead time critical supplies is a prudent decision from management. It also feels it is reflective of its strengthened financial position and improved visibility over near-term sales opportunities. The Electro Optic Systems share price is trading at $1.59 on Friday afternoon.

Another note out of Bell Potter reveals that its analysts have retained their speculative buy rating on this biotechnology company's shares with a significantly improved price target of $1.40 (from 58 cents previously). Bell Potter notes that the FDA has used carefully chosen words to inform Mesoblast that the available clinical data from its Phase 3 study MSB-GvHD001 in children with steroid refractory acute graft versus host disease (SR a GvHD) appears sufficient to support a resubmission of the Biological Licence Application (BLA) for Remestemcel. It points out that the timing of the correspondence coincides with refreshed leadership at the newly formed Office of Therapeutic Products at the FDA. In light of this, the broker has renewed confidence for a prospective approval for Remestemcel later this year. It feels that a first approval may represent a gateway to a series of label expansions in the ensuing period. The Mesoblast share price is fetching 86.7 cents on Friday.

Analysts at Morgan Stanley have retained their overweight rating and $17.05 price target on this insurance giant's shares. This follows news that the company has signed an agreement to sell its New Zealand life insurance business to Resolution Life for approximately $375 million. The broker feels the selling price is fair and expects it to result in a simplified business structure. Combined with the Suncorp Bank sale to ANZ Group Holdings Ltd (ASX: ANZ), it believes there could be some big capital returns to come in the near future. The Suncorp share price is on course to end the week at $16.25.