Education
LessonIntroductory data science · 55 min

Catalog Data Quality Check

Build a small, honest quality report from a catalog subset. Missing and conflicting values are findings, not values to silently replace.

data-qualitymissing-dataprovenancereproducibility
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Overview

A public catalog is useful because it exposes its limitations. Empty fields can result from unavailable coverage, unresolved source disagreement, or a field that does not apply. They must not be turned into invented values.

This lesson uses a small subset so students can audit every row. The goal is not to produce a flattering chart. The goal is to publish a result that another person can reproduce and challenge.

At a glance

Learning objectives

  • Separate missing, unknown, and conflicting data from a valid zero or empty value.
  • Create a small data-quality summary with documented filters and access date.
  • Keep raw identifiers when cleaning a subset so results remain auditable.

Prerequisites

  • Basic spreadsheet filtering or dataframe skills.

Required software

  • OrbitalWiki datasets page and a spreadsheet or notebook.

Dataset version

OrbitalWiki live catalog. Record the dataset-release label from /datasets when available, or the exact access date for a live lookup.

Student instructions

  1. 1Download one published catalog subset from /datasets, or record the exact filters and date if using the live catalog.
  2. 2Select up to 100 rows. Keep NORAD ID, name, and any fields you analyse.
  3. 3For each analysed field, count populated values and missing values. Do not replace missing values with zero, “unknown”, or a made-up category.
  4. 4Choose five rows with missing or uncertain fields. Inspect their record pages and note the source or confidence information that is available.
  5. 5Publish a one-page quality note listing the release or access date, filters, fields, counts, and one limitation.

Expected output

  • A documented subset and a field-completeness table.
  • A quality note that states one limitation without hiding it.
[teacher]

Teacher materials, not student-facing

Teaching notes

  • Do not grade students on maximizing completeness. Grade them on preserving meaning and documenting exclusions.
  • A result based on a changing live catalog is not a fixed historical trend. Require the dataset release or access date.

Answer key

Is a blank field equal to zero?
No. A blank is an observation about availability or applicability, not a numerical value.
What makes the subset reproducible?
The release label or access date, explicit filters, field list, and retained identifiers.

How to cite

Cite the exact dataset release URL when used. For a live query, cite the query parameters, access date, and record URLs for quoted examples.

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