Satcom Status Tracker

Introduction:

Satellite communications planning depends on knowing whether an orbital record is current enough to support the next decision. A spacecraft name can look familiar while its latest Two-Line Element set, usually shortened to TLE, is too old for pointing, scheduling, or even a confident status screen. Element age, orbit geometry, and available operating context all affect how much trust belongs in a quick check.

A TLE is a compact orbital snapshot. It carries the catalog number, epoch time, inclination, eccentricity, mean motion, and other values needed by standard orbit models. For satcom work, those values help answer practical questions such as which candidate is in low Earth orbit, which entry is near geostationary height, which record has gone stale, and which match needs another source before anyone treats it as active.

Age matters because a TLE is tied to its epoch. The farther a planning time moves away from that epoch, the more room there is for drag, maneuvers, modeling limits, or catalog updates to make a quick estimate less useful. Fresh orbital elements do not prove that a satellite is transmitting or healthy, but stale elements can make otherwise good status information unsafe for antenna pointing or contact timing.

Orbit class also matters because satcom records span very different regimes. A low Earth orbit spacecraft can move quickly across a local sky and needs recent elements for pass timing. A geostationary spacecraft changes more slowly from a ground observer's point of view, but an approximate GEO label still does not confirm station-keeping, transponder availability, licensing, or link budget readiness.

A good satcom status screen is therefore a triage step. It narrows a candidate list, flags stale orbital data, separates current-looking rows from archive records, and tells the user when a second operational source is needed. It should not be read as a precision ephemeris, a live telemetry monitor, or proof that a spacecraft can support a specific link.

Technical Details:

Two-Line Element data stores mean orbital elements in a fixed text format. The fields most useful for quick satcom screening are the NORAD catalog number, the epoch, line 2 inclination, line 2 eccentricity, and line 2 mean motion. Mean motion is expressed as revolutions per day, so it can be converted to an orbital period and then used for a circular-orbit altitude estimate.

The altitude estimate is intentionally simple. It treats mean motion as the main quantity and applies Kepler's third-law relationship with a fixed Earth gravitational parameter and Earth radius. That gives a useful sort and sanity check across many returned satellites, but it is not the same as running SGP4 propagation to a target time and ground location.

The main calculation converts mean motion to angular speed, derives semi-major axis, then subtracts Earth radius to estimate altitude.

For a mean motion of about 15.5 rev/day, the period is roughly 93 minutes. The same value converts to an altitude near the low Earth orbit range after subtracting the Earth radius. A much smaller mean motion, such as about 1 rev/day, lands near the geostationary altitude range. These examples explain why mean motion is a fast way to separate orbital families, even before doing a precise pass prediction.

Orbit class boundaries are fixed and altitude-based. The comparison uses kilometers above the Earth radius estimate, so boundary rows should be read as screening labels rather than official orbital classifications.

Freshness and readiness are separate outputs. Freshness describes the age band of the TLE epoch. Planning readiness converts that same age into a caution label for pointing or scheduling. The freshness policy controls which rows remain in the result set, while the freshness band still follows the same 1, 2, and 7 day breakpoints.

The freshness policy adds a second guardrail. Strict keeps the effective maximum age at 2 days, balanced keeps it at 7 days, and archive keeps it at 14 days. The manual TLE freshness field can tighten that cap, but it cannot loosen the active policy. Unknown-age rows are allowed through the age filter so they can be inspected instead of silently disappearing.

SatNOGS enrichment adds operating context after TLE parsing. When present, an alive status becomes Active, future becomes Planned, dead becomes Non-operational, and re-entered or decayed records become Re-entered. Operator, country, website, last SatNOGS update, and frequency-violator flags are merged into the returned row when available. If the overlay call fails or no record exists, the TLE-derived orbit and age fields remain available and the status line explains the partial coverage.

The resulting data should be treated as deterministic triage from public orbital records plus optional community database context. It does not measure live RF signal, run a pass prediction for a ground station, verify spacecraft commandability, or confirm that any transmitter is usable for a given regulatory or operational plan.

Everyday Use & Decision Guide:

Use a NORAD catalog number when you have one. A 3 to 6 digit search first tries a direct catalog lookup, which avoids many ambiguous name matches. Name or constellation searches are better when you are exploring a fleet, but they can return planned, historical, or similarly named spacecraft, so the matches table becomes part of the check.

The constellation preset is a starter, not a final answer. Starlink, OneWeb, Iridium NEXT, Globalstar, Inmarsat, Intelsat, SES, and Telesat or Anik presets load common search text and reset the page offset. After that, the active freshness policy still controls the maximum age. For current link planning, leave balanced at 7 days only if the job can tolerate caution rows; use strict when stale elements should disappear quickly.

Keep the result cap small when SatNOGS overlay is enabled. The cap accepts 1 to 40 records, and each overlay row needs an additional status lookup. A cap of 10 is enough for most candidate screens. Raise it when a broad keyword hides the target, or use the page offset when the first page is dominated by the wrong constellation shell.

Turn on Only active only when SatNOGS overlay is available and you are trying to hide dead or re-entered spacecraft. Leave it off for historical cleanup, archive reviews, or cases where a missing SatNOGS record should remain visible. Keep decayed entries is useful for launch-campaign checks and catalog cleanup, not for live planning.

Use the output surfaces for different checks:

• Status is the selected satellite audit: Status, Orbit class, Altitude, Inclination, Period, Mean motion, TLE age, Freshness band, Planning readiness, and the active policy.
• Matches is the comparison view for near-duplicates and fleet searches.
• TLE is the exact element text for the selected row.
• Altitude Stack separates returned satellites by estimated altitude and orbit family.
• Freshness Ladder makes aging and stale rows obvious against the 1, 2, and 7 day marks.
• Link Planning Brief turns stale counts, auto-refresh state, and overlay gaps into follow-up actions.

The common misread is treating Active as mission-ready. Active comes from SatNOGS status context, while Ready for pointing comes from TLE age. A row can be Active and still need a newer element set, or have a fresh TLE and still need operational confirmation from another source.

Step-by-Step Guide:

Run the check in the order that protects the result from avoidable ambiguity.

1. Enter a Satellite / NORAD search value. Use a catalog number such as 25544 for an exact lookup, or a keyword such as STARLINK, OneWeb, Iridium, or SES when you want candidates.
2. Choose a Constellation preset only if it matches your search intent. Custom keeps your manual query, while a preset rewrites the query and resets the page offset.
3. Set Result cap and TLE freshness. Keep the cap near 10 for quick screens, and use the freshness field only to make the active policy stricter.
4. Pick the Freshness policy. Strict gives an effective cap of 2 days, balanced gives 7 days, and archive gives 14 days.
5. Enable SatNOGS overlay when operator, country, or alive/dead context matters. If the overlay is off, Status will read TLE only and active-only filtering is not available.
6. Use Sort by after results appear. Newest epoch first is best for current screening, while altitude, inclination, period, and freshness help compare a mixed candidate set.
7. If the page reports No satellites found for that query, simplify the name or switch to NORAD ID. If it reports No entries matched after applying the filters, loosen stale-only or active-only filters, or use archive policy for older records.
8. Review Status, Matches, Altitude Stack, Freshness Ladder, and Link Planning Brief before copying or downloading data for follow-up work.

Interpreting Results:

Read TLE age first when the task involves pointing, pass timing, or near-term contact planning. Fresh (<=1d) and Monitor (1-2d) both show Ready for pointing, but the Monitor band should still prompt a close-in refresh when precision matters. Aging (2-7d) supports triage, and Stale (>7d) should be refreshed before use.

Read Orbit class and Altitude as geometry hints. LEO, MEO, GEO belt, and HEO are assigned from an approximate altitude estimate, so they are useful for sorting a list and catching obvious mismatches. They do not confirm a pass over a ground station, a usable elevation window, or a particular antenna requirement.

Read Status as overlay context. Active, Planned, Non-operational, Re-entered, Unknown, or TLE only should be checked against the SatNOGS overlay note, SatNOGS updated value, and the presence or absence of operator and country fields. A missing overlay does not mean the spacecraft is healthy; it means the TLE-derived fields are carrying the screen without that extra status context.

Use the Link Planning Brief as a stop-and-check summary. If it says stale targets need element refresh, update the TLE source before committing windows. If it warns about partial SatNOGS coverage, verify the candidate in another operations source before relying on the status label.

Worked Examples:

Narrowing a LEO broadband target

A user enters STARLINK-3000, keeps Result cap at 10, uses strict policy, and leaves Sort by on Newest epoch first. If the selected Status row shows Orbit class LEO, Altitude near 550 km, TLE age 0.6 days, Freshness band Fresh (<=1d), and Planning readiness Ready for pointing, the record is suitable for first-pass contact planning. It still needs a pass predictor and ground-station geometry before any antenna schedule is accepted.

A borderline TLE age under balanced policy

A planner searches a known NORAD ID and receives a TLE age of 1.8 days. The Freshness band should read Monitor (1-2d), while Planning readiness still reads Ready for pointing because readiness stays green through 2 days. The right follow-up is to recheck close to operation time, not to discard the row immediately.

Archive review for an older GEO record

A GEO operator keyword returns a satellite with estimated Altitude around 35786 km, Orbit class GEO belt, and TLE age 10.4 days. Under balanced policy, that row is filtered out by the 7 day cap. Switching to archive policy can keep it visible with Freshness band Stale (>7d) and Planning readiness Refresh before use, which is appropriate for archive comparison but not for current link timing.

Troubleshooting an empty result after filters

A user enables SatNOGS overlay, Only active, Show stale only, and a strict freshness policy, then sees No entries matched after applying the filters. The controls are asking for rows that are both active and at least aging while also capped at 2 days, so the filter set can exclude everything. Turning off Show stale only or switching to archive policy lets older rows reappear for inspection.

FAQ:

Glossary:

TLE

A Two-Line Element set, the compact orbital record used as the main source for epoch, inclination, eccentricity, and mean motion.

NORAD catalog number

The numeric identifier used to request or compare a specific Earth-orbiting object.

Epoch

The reference time for the TLE values. TLE age is measured from this time.

Mean motion

The number of revolutions per day recorded in line 2 of the TLE and used here to estimate period and altitude.

Inclination

The orbit angle relative to the equator, shown in degrees in the Status row.

Freshness band

The TLE age label, such as Fresh (<=1d), Monitor (1-2d), Aging (2-7d), or Stale (>7d).

Planning readiness

The age-based caution label that says whether the TLE is ready, cautionary, stale, or unknown for planning.

SatNOGS overlay

The optional status context that can add active, planned, non-operational, re-entered, operator, country, and update fields.

References:

• Frequently Asked Questions: Two-Line Element Set Format, CelesTrak, January 1998.
• Revisiting Spacetrack Report #3: Rev 3, AIAA and CelesTrak.
• SatNOGS DB API documentation, Libre Space Foundation.
• SatNOGS DB, Libre Space Foundation.