wip(mobile): checkpoint engine and experience round three in progress

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01VVYRAqiQj9Y1V9ZfG1RcDH

mobile/globe/sky.js

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+/**
+ * "Your sky now" (DESIGN.md §12.3): what is above a person this minute.
+ * Aircraft within ~50 km from the live ADS-B feeds (fetching a regional
+ * snapshot around the person when the current one does not cover them),
+ * satellites above the horizon from CelesTrak elements (SGP4), and the ISS
+ * with its next pass.
+ */
+import { twoline2satrec } from 'satellite.js';
+import { findNextIssPass, lookAnglesAt } from '../../src/data/issPass.js';
+import { haversineKm, subsolarPoint } from './geo.js';
+import { bearingDeg } from './gazetteer.js';
+
+const R = 6_371_000;
+const D2R = Math.PI / 180;
+const ISS_NORAD = '25544';
+
+function elevationDeg(distM, altM) {
+  // Flat-earth elevation corrected for the curvature drop over distM.
+  const drop = (distM * distM) / (2 * R);
+  return Math.atan2(altM - drop, distM) / D2R;
+}
+
+function sunElevation(lat, lon, ms) {
+  const s = subsolarPoint(ms);
+  const cosZ =
+    Math.sin(lat * D2R) * Math.sin(s.lat * D2R) +
+    Math.cos(lat * D2R) * Math.cos(s.lat * D2R) * Math.cos((lon - s.lon) * D2R);
+  return 90 - Math.acos(Math.max(-1, Math.min(1, cosZ))) / D2R;
+}
+
+const satCache = { stamp: '', sats: [] };
+function satrecs(feeds) {
+  const groups = ['stations', 'visual'];
+  const stamp = groups.map((g) => feeds[g].updatedAt).join(':');
+  if (stamp === satCache.stamp) return satCache.sats;
+  const seen = new Set();
+  const sats = [];
+  for (const g of groups)
+    for (const e of feeds[g].data?.entries || []) {
+      const id = e.line1.slice(2, 7).trim();
+      if (seen.has(id)) continue;
+      seen.add(id);
+      try {
+        sats.push({
+          id,
+          name: e.name.trim(),
+          satrec: twoline2satrec(e.line1, e.line2),
+        });
+      } catch {
+        /* malformed */
+      }
+    }
+  satCache.stamp = stamp;
+  satCache.sats = sats;
+  return sats;
+}
+
+export async function skyNow(feeds, { lon, lat }, { km = 50 } = {}) {
+  if (!Number.isFinite(lon) || !Number.isFinite(lat))
+    throw new TypeError('skyNow needs lon and lat');
+  const now = Date.now();
+  // Aircraft: whatever the feeds hold near the person, plus a regional
+  // snapshot around them when nothing current covers the spot.
+  const lists = [];
+  const flights = feeds.flights.data;
+  if (flights?.records) lists.push(flights.records);
+  if (feeds.military.data?.records) lists.push(feeds.military.data.records);
+  for (const e of feeds.regionalFlights.entries?.() || [])
+    if (e.data?.records) lists.push(e.data.records);
+  const covered =
+    flights &&
+    (!flights.regional ||
+      (flights.anchor &&
+        haversineKm(lat, lon, flights.anchor.lat, flights.anchor.lon) < 300));
+  if (!covered) {
+    const key = `sky:${lat.toFixed(1)}:${lon.toFixed(1)}`;
+    const reg = await Promise.race([
+      feeds.regionalFlights.get(key, { lat, lon }).catch(() => null),
+      new Promise((r) => setTimeout(() => r(null), 9000)),
+    ]);
+    if (reg?.records) lists.push(reg.records);
+  }
+  const seen = new Set();
+  const aircraft = [];
+  for (const list of lists)
+    for (const r of list) {
+      if (seen.has(r.id) || r.onGround) continue;
+      if (Math.abs(r.lat - lat) > km / 100 + 0.2) continue;
+      const d = haversineKm(lat, lon, r.lat, r.lon);
+      if (d > km) continue;
+      seen.add(r.id);
+      aircraft.push({
+        id: `${r.military ? 'military' : 'flights'}:${r.id}`,
+        title: r.callsign || r.id.toUpperCase(),
+        kind: r.military
+          ? 'military'
+          : r.helicopter
+            ? 'helicopter'
+            : 'aircraft',
+        lon: r.lon,
+        lat: r.lat,
+        altM: Math.round(r.altM ?? 0),
+        distanceKm: Math.round(d * 10) / 10,
+        elevationDeg: Math.round(elevationDeg(d * 1000, r.altM ?? 0) * 10) / 10,
+        azimuthDeg: Math.round(bearingDeg(lat, lon, r.lat, r.lon)),
+        headingDeg: r.heading ?? null,
+        speedMps: r.speed ?? null,
+        squawk: r.squawk || null,
+      });
+    }
+  aircraft.sort((a, b) => b.elevationDeg - a.elevationDeg);
+
+  // Satellites above the horizon.
+  // Cached elements answer at once; a cold catalog gets 4 s.
+  await Promise.race([
+    Promise.allSettled([feeds.stations.get(), feeds.visual.get()]),
+    new Promise((r) => setTimeout(r, 4000)),
+  ]);
+  const satellites = [];
+  let iss = null;
+  for (const s of satrecs(feeds)) {
+    const look = lookAnglesAt(s.satrec, now, lat, lon);
+    if (!look) continue;
+    if (s.id === ISS_NORAD) iss = { s, look };
+    if (look.elevDeg <= 0) continue;
+    const p = look.satECI;
+    satellites.push({
+      id: `satellites:${s.id}`,
+      title: s.name,
+      norad: s.id,
+      altKm: p ? Math.round(Math.hypot(p.x, p.y, p.z) - 6371) : null,
+      elevationDeg: Math.round(look.elevDeg * 10) / 10,
+      azimuthDeg: Math.round(look.azDeg),
+    });
+  }
+  satellites.sort((a, b) => b.elevationDeg - a.elevationDeg);
+
+  const sunEl = sunElevation(lat, lon, now);
+  let issOut = {
+    visibleNow: false,
+    elevationDeg: null,
+    azimuthDeg: null,
+    nextPass: null,
+  };
+  if (iss) {
+    const pass = findNextIssPass({
+      satrec: iss.s.satrec,
+      latDeg: lat,
+      lonDeg: lon,
+      fromMs: now,
+      minElevDeg: 10,
+      horizonHours: 36,
+    });
+    issOut = {
+      visibleNow: iss.look.elevDeg > 10 && sunEl < -6,
+      aboveHorizon: iss.look.elevDeg > 0,
+      elevationDeg: Math.round(iss.look.elevDeg * 10) / 10,
+      azimuthDeg: Math.round(iss.look.azDeg),
+      nextPass: pass
+        ? {
+            start: pass.riseMs,
+            max: pass.maxElevMs,
+            end: pass.setMs,
+            maxElevationDeg: Math.round(pass.maxElevDeg),
+            riseAzimuthDeg: Math.round(pass.riseAzDeg ?? 0),
+            visible: Boolean(pass.visible),
+          }
+        : null,
+    };
+  }
+  return {
+    at: now,
+    observer: { lon, lat },
+    sunElevationDeg: Math.round(sunEl * 10) / 10,
+    aircraft: aircraft.slice(0, 60),
+    satellites: satellites.slice(0, 40),
+    iss: issOut,
+    sources: ['OpenSky Network / adsb.lol (ODbL)', 'CelesTrak GP data, SGP4'],
+  };
+}