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The Spacecraft Schedule File (SSF) is a flat ASCII text format that lists every operationally relevant activity for a spacecraft over a chosen window — ground station passes, eclipse entries and exits, apsis crossings, node crossings, and South Atlantic Anomaly (SAA) transits — in a single chronologically sorted document. The format is derived from the CCSDS 902.1 Simple Schedule data model and uses Keyword-Value Notation (KVN) so the file is readable by humans and trivially parsed by downstream tooling.
VALAR emits SSF files from the Export Schedule dialog on the Burn Plan Timeline and the passes timeline.
Key Components
An SSF file is composed of three KVN blocks separated by blank lines:
- Header Block: format version, free-form comments, generation timestamp, originator
- Schedule Metadata Block: spacecraft identifier and the inclusive UTC window the schedule covers
- Activity Blocks: one block per activity, sorted ascending by start epoch, each containing the activity type, start and (when applicable) stop epochs, and any type-specific metadata keywords
The Header Block opens the file and identifies the document and its origin.
| Keyword | Description | Example |
|---|
| CCSDS_SSF_VERS | The format version. Always 1.0 for VALAR-emitted files. | 1.0 |
| COMMENT | Optional free-form comment lines. Multiple COMMENT lines may appear. | Generated for operations handover |
| CREATION_DATE | UTC timestamp at which the file was generated, in ISO-8601 format. | 2026-04-13T08:00:00.000Z |
| ORIGINATOR | The system or organization that produced the file. Always VALAR for VALAR-emitted files. | VALAR |
| Keyword | Description | Example |
|---|
| SPACECRAFT_ID | The spacecraft this schedule belongs to. | MATTIA |
| SCHEDULE_START | Inclusive start of the schedule window in UTC ISO-8601. | 2026-04-13T00:00:00Z |
| SCHEDULE_STOP | Inclusive end of the schedule window in UTC ISO-8601. | 2026-04-15T00:00:00Z |
Activity Blocks
Each activity is its own block containing ACTIVITY_TYPE, ACTIVITY_START, an optional ACTIVITY_STOP, and any type-specific metadata.
| Keyword | Description |
|---|
| ACTIVITY_TYPE | The activity category (see Activity Types below). |
| ACTIVITY_START | UTC start epoch of the activity in ISO-8601. |
| ACTIVITY_STOP | UTC stop epoch of the activity in ISO-8601. Optional — see below. |
| Type-specific metadata | Additional keywords that depend on ACTIVITY_TYPE (for example DURATION_S on SAA_ENTRY). |
ACTIVITY_START epoch regardless of type. A ground pass and an eclipse entry that fall in the same minute are interleaved by start time, not grouped by category.
Optional ACTIVITY_STOP. The ACTIVITY_STOP keyword is present for activities that have a duration (ground passes, umbra and penumbra bands, SAA transits) and is omitted for instantaneous events (apsis crossings, node crossings, and SAA_EXIT). When ACTIVITY_STOP is omitted you can treat the activity as a single-epoch marker at ACTIVITY_START.
Activity Types
The ACTIVITY_TYPE keyword takes one of exactly 11 case-sensitive values:
| Type | Description | Has ACTIVITY_STOP? |
|---|
| GROUND_PASS | Ground station visibility pass (AOS to LOS). | Yes |
| PENUMBRA_ENTRY | Spacecraft enters Earth’s penumbra (partial shadow). | Yes |
| UMBRA_ENTRY | Spacecraft enters Earth’s umbra (full shadow). | Yes |
| UMBRA_EXIT | Spacecraft exits Earth’s umbra. | Yes |
| PENUMBRA_EXIT | Spacecraft exits Earth’s penumbra. | Yes |
| SAA_ENTRY | Spacecraft enters the South Atlantic Anomaly. Carries the band transit duration as the DURATION_S metadata keyword and a synthesized ACTIVITY_STOP. | Yes |
| SAA_EXIT | Spacecraft exits the South Atlantic Anomaly. Point event; carries no metadata. The transit duration is recorded on the paired SAA_ENTRY activity. | No |
| PERIAPSIS | Spacecraft reaches closest approach to Earth. | No |
| APOAPSIS | Spacecraft reaches farthest point from Earth. | No |
| ASCENDING_NODE | Spacecraft crosses the equatorial plane heading north. | No |
| DESCENDING_NODE | Spacecraft crosses the equatorial plane heading south. | No |
KVN Encoding
SSF uses a fixed Keyword-Value Notation:
- Each keyword occupies a 24-character left-justified column followed by
= and the value.
- Values are plain ASCII text encoded as UTF-8. There is no quoting or escaping.
- Blocks are separated by a single blank line.
- Within an activity block, type-specific metadata keywords appear in alphabetical order after
ACTIVITY_START and ACTIVITY_STOP.
Common Use Cases
- Operations scheduling: Hand a single file to flight controllers covering every contact, eclipse, and high-radiation transit for the upcoming window.
- Automated handover: Feed the schedule into ground-segment automation to pre-arm tracking, payload, and safe-mode logic at the right times.
- Downstream tooling: Consume the schedule from third-party planning tools or in-house scripts using any KVN parser without bespoke schema work.
Worked Example
The example below shows a 2-day schedule for a single LEO spacecraft. It contains four representative activity blocks: a ground pass with an explicit stop, an umbra entry band, an instantaneous periapsis crossing, and an SAA entry carrying its DURATION_S metadata.
CCSDS_SSF_VERS = 1.0
COMMENT Generated for operations handover
CREATION_DATE = 2026-04-13T08:00:00.000Z
ORIGINATOR = VALAR
SPACECRAFT_ID = MATTIA
SCHEDULE_START = 2026-04-13T00:00:00Z
SCHEDULE_STOP = 2026-04-15T00:00:00Z
ACTIVITY_TYPE = GROUND_PASS
ACTIVITY_START = 2026-04-13T03:42:18Z
ACTIVITY_STOP = 2026-04-13T03:51:04Z
GROUND_STATION_ID = SVALBARD-01
MAX_ELEVATION_DEG = 72.4
ACTIVITY_TYPE = UMBRA_ENTRY
ACTIVITY_START = 2026-04-13T04:18:32Z
ACTIVITY_STOP = 2026-04-13T04:53:11Z
ACTIVITY_TYPE = PERIAPSIS
ACTIVITY_START = 2026-04-13T05:11:47Z
ACTIVITY_TYPE = SAA_ENTRY
ACTIVITY_START = 2026-04-13T06:24:09Z
ACTIVITY_STOP = 2026-04-13T06:32:48Z
DURATION_S = 519.0
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