Starfleet ranks & rates
2351-2365

Commissioned officers
Fleet Admiral
Admiral
Vice Admiral		VADM Aaron TNG Conspiracy
Rear Admiral (upper half)		RADM Savar TNG Conspiracy
Rear Admiral (lower half)		RDML Gregory Quinn TNG Conspiracy
Captain		CAPT Jean-Luc Picard TNG Conspiracy
Commander		CDR Beverly Crusher TNG Coming of Age
Lieutenant Commander		LCDR Dexter Remmick TNG Coming of Age
Lieutenant		LT Logan TNG The Arsenal of Freedom
Lieutenant Junior Grade		LTJG Geordi La Forge TNG The Arsenal of Freedom
Ensign		ENS Haskell TNG Where Silence Has Lease
Enlisted personnel
Master Chief Petty Officer Senior Chief Petty Officer Chief Petty Officer		CPO Gladstone TNG The Child
Petty Officer 1st class Petty Officer 2nd class Petty Officer 3rd class Crewman 1st class Crewman 2nd class Crewman 3rd class	no insignia	CN Rondon TNG Coming of Age
Provisional officers
Captain
Commander
Lieutenant Commander
Lieutenant
Lieutenant Junior Grade		LTJG Kosinski TNG Where No One Has Gone Before
Ensign
Chief Petty Officer

Annotations & Trivia:

• No official information regarding the admiralty rank insignia has been released, so it's pretty much an educated guess on my part based on the assumption that the insignia mirror current U.S. Navy admiralty rank stripes. Thus, the braid would be equivalent to the Navy 2 inch stripe and the pips equivalent to the 1/2 inch stripes.
• My decision to call the most junior admiral rank "Rear Admiral (lower half)" instead of "Commodore" is based on three clues:
  1. The TNG rank pips have far more in common with current U.S. Navy rank stripes than with TOS rank stripes. Thus, it's not unreasonable to assume that TPTB not only adopted the rank scheme but also the terminology.
  2. The only two Starfleet officers who wore Admiralty braid without pips, Mark Jameson and Gregory Quinn, were referred to as "Admiral".
  3. In the TNG episode "Coming of Age", Picard was offered a promotion from captain to admiral.
• For my rationalisation of the simplified enlisted rates structure please refer to the annotations on the 2366-2372 ranks & rates page.
• The provisional rank markers were only used in the TNG episode "Where No One Has Gone Before". It has been suggested that they might denote warrant officers. However, considering the lack of an Starfleet insignia on Kosinski's uniform and his very disrespectful behaviour towards superior officers, I find it far more likely that he was a civilian with a provisional commission for the duration of his assignment aboard Starfleet vessels.