Don't know about "Pertama" but for Muda, Madya and Utama you could use Junior, Middle and Senior, and Peneliti is probably Researcher.

For comparison/ reference, here are some equivalents for other civil service ranks (sorry, I don't remember the source):

No. Rank Class Level
1 Juru Muda Junior Clerk I a
2 Juru Muda Tingkat I First Class Junior Clerk I b
3 Juru Clerk I c
4 Juru Tingkat I First Class Clerk I d
5 Pengatur Muda Junior Supervisor II a
6 Pengatur Muda Tingkat I First Class Junior Supervisor II b
7 Pengatur Supervisor II c
8 Pengatur Tingkat I First Class Supervisor II d
9 Penata Muda Junior Superintendent III a
10 Penata Muda Tingkat I First Class Junior Superintendent III b
11 Penata Superintendent III c
12 Penata Tingkat I First Class Superintendent III d
13 Pembina Administrator IV a
14 Pembina Tingkat I First Class Administrator IV b
15 Pembina Utama Muda Junior Administrator IV c
16 Pembina Utama Madya Middle Administrator IV d
17 Pembina Utama Senior Administrator IV e