diff --git a/docs/disc-image.md b/docs/disc-image.md
index 8af92c9..12aa01b 100644
--- a/docs/disc-image.md
+++ b/docs/disc-image.md
@@ -9,5 +9,12 @@
 | SHA-1 | `4abe30077c2b449ea68239083df7932d47ae0b69` |
 | 2352-byte sectors | 294,018 exactly |
 | CUE sheet | Not currently available |
+| ISO9660 volume ID | `SCUS94640` |
+| Logical block size | 2048 bytes |
+| Volume space size | 294,018 logical blocks |
 
-The image is ignored and must never be staged. Its SHA-1 identifies the local input only; it does not establish a redump match, track layout, or game serial. Phase 0 must determine whether a matching CUE can be recovered or whether a single-track MODE2/2352 interpretation is supported by the bytes.
+## Characterization (Phase 0 T1)
+
+The raw sector sync/header bytes identify MODE2/2352 sectors. The ISO9660 primary volume descriptor is at raw sector 16, byte offset 24: type `1`, magic `CD001`, version `1`. The volume-space size equals the full image's 294,018 physical sectors, so a 2048-byte ISO filesystem can be read directly from this BIN using a 2352-byte stride and user-data offset 24.
+
+A CUE is **not required** for filesystem or executable extraction. Preserve or recover a matching CUE later for exact track metadata, emulator setup, and any disc-rebuild work. The image is ignored and must never be staged. Its SHA-1 identifies the local input only; it does not establish a redump match, complete track layout, or broader disc provenance.
diff --git a/docs/formats.md b/docs/formats.md
index 65a7b6e..f03fe57 100644
--- a/docs/formats.md
+++ b/docs/formats.md
@@ -2,12 +2,18 @@
 
 ## Disc image
 
-The current USA disc image is exactly 294,018 sectors of 2352 bytes. This establishes only its physical-sector size. The following remain unverified:
+The current USA disc image is exactly 294,018 sectors of 2352 bytes. Phase 0 T1 verified these facts from sectors 0, 16, and 17:
 
-- track count and track boundaries;
-- MODE1 versus MODE2 sector interpretation;
-- ISO9660 volume-descriptor location and filesystem layout;
+- sector sync bytes are `00 FF×10 00` and the mode byte is `02` (MODE2);
+- the 2048-byte user-data area begins at byte offset 24 of each raw sector;
+- raw sector 16 + 24 is an ISO9660 primary volume descriptor: type `1`, `CD001`, version `1`, volume ID `SCUS94640`;
+- raw sector 17 + 24 is the ISO9660 volume-descriptor terminator: type `255`, `CD001`, version `1`;
+- ISO logical blocks are 2048 bytes and the PVD's volume-space size is 294,018, equal to the image sector count.
+
+Filesystem/executable extraction may therefore read the BIN with a 2352-byte stride and offset 24 without a CUE. The following remain unverified:
+
+- track count and track boundaries beyond the data filesystem;
 - executable filename and format;
 - archive, compression, audio, video, and overlay formats.
 
-Phase 0/1 must record observations and evidence here. Do not infer format details from other Syphon Filter games or other regions.
+Do not infer later format details from other Syphon Filter games or other regions.
diff --git a/phase-ends/CURRENT_PHASE.md b/phase-ends/CURRENT_PHASE.md
index 05ead1d..30bd311 100644
--- a/phase-ends/CURRENT_PHASE.md
+++ b/phase-ends/CURRENT_PHASE.md
@@ -5,7 +5,7 @@
 ## Tasks
 
 - [x] T0 — Establish the Git firewall and project-state baseline: initialize Git; place the local image under ignored `disks/`; write governance, setup, format, memory-map, and Phase 0 state documents; verify no ROM-derived material is staged; make the first governance commit.
-- [ ] T1 — Characterize the local 2352-byte image safely: inspect sector 16 and determine whether an ISO9660 filesystem is present; determine whether a CUE is required; record evidence in `docs/formats.md`.
+- [x] T1 — Characterize the local 2352-byte image safely: inspect sector 16 and determine whether an ISO9660 filesystem is present; determine whether a CUE is required; record evidence in `docs/formats.md`. Verified MODE2/2352, ISO9660 PVD at sector 16 + 24, volume `SCUS94640`, 2048-byte blocks, and 294,018 blocks; a CUE is unnecessary for filesystem extraction.
 - [ ] T2 — Create and approve Phase 1's extraction/import plan.
 
 ## Known input
@@ -16,4 +16,4 @@
 
 ## Session checkpoint
 
-T0 is complete: the governance-only initial commit contains no ROM-derived material; `.gitignore` excludes the disc image and generated paths. The next action is T1: inspect sector 16 safely and determine the disc filesystem/CUE requirements.
+T0 and T1 are complete. The first commit contains no ROM-derived material; `.gitignore` excludes the local image and generated paths. T1 verified MODE2/2352 and ISO9660 sector-16 metadata, so Phase 1 can extract from the BIN directly. The next action is T2: create and approve the Phase 1 extraction/import plan.