Recover a mission from its data

An analog recording, a film ionogram, its digital scan and an extracted table are different artifacts. A scan can preserve features that a particular extraction method rejects. A table makes computation easier, but without the scan and processing choices it can be difficult to diagnose a mistaken point.

The CSA’s restoration account reports 1,612,104 scanned Alouette 1 ionograms and 693,677 fully read and processed images by 2023. Those numbers describe different processing stages. They do not mean the mission observed only that fraction of Earth, or that every remaining scan contains no recoverable information.

NASA’s historical tape-restoration selection emphasized geographic coverage and particular scientific interests within a much larger tape collection. A later film-rescue effort recovered another route to Alouette 1 observations. A count from one restoration project is not automatically the total surviving record of a mission.

In an original example, archive A contains 900 winter observations from a polar station and 100 summer observations from an equatorial station. Its overall average mixes location and season. Comparing that average directly with a balanced modern sample could create an apparent change caused by selection. First match the sampled conditions or use a justified method to account for their differences.

A scan and a table preserve different information

A useful release connects each extracted measurement to the source scan, spacecraft, time, station, units, software version and quality flags. Checksums help detect changed bytes; they do not establish that a plotted trace is physically correct. Keep an unmodified source and describe any corrections rather than silently replacing the only copy.

For an original rescue test, hand-check a varied sample: faint and strong traces, different stations and multiple metadata formats. Report which cases fail as well as an overall success rate. If a later algorithm improves the result, retain enough information to compare versions. The goal is an archive that can answer new questions without obscuring how its evidence was produced.