diff --git a/core/presentation/src/main/res/values/strings.xml b/core/presentation/src/main/res/values/strings.xml
index c458cb30..ed1b585f 100644
--- a/core/presentation/src/main/res/values/strings.xml
+++ b/core/presentation/src/main/res/values/strings.xml
@@ -56,13 +56,14 @@
         \n\nPlease update the database at least weekly to get accurate predictions.</string>
     <string name="pass_whatsnew_title" translatable="false">What\'s new in Look4Sat</string>
     <string name="pass_whatsnew_message" translatable="false">
-        * Added AMSAT status tracking page by MCKero6423 (#234)
-        \n* Tweaked Radar track on reposition by atsunatsu (#235)
-        \n* Tweaked linear transponder calc by atsunatsu (#236)
-        \n* Added saving per-sat doppler offset by atsunatsu (#237)
-        \n* Added custom freq offset setting to network reporting
-        \n* Added ability to customize data sources via import
-        \n* Fixed star chart in README by PingouinFerreux (#240)
+        * Tweaked sunrise/sunset calculations, added tests by atsunatsu (#241)
+        \n\n* Overhauled sources import, added HTTP status by wty2019wty (#242)
+        \nSources now have priority - the top ones define satellite names and transceiver data.
+        \nYou can enable/disable sources and restore defaults via the Satellite data import dialog.
+        \n\n* Localized AMSAT status screen for Chinese by atsunatsu (#245)
+        \n\n* Extracted hardcoded UI strings to resources by TianhengZhuang (#247)
+        \n\n* Added AMSAT satellite status reports submission by atsunatsu (#248)
+        \n\n* Slightly optimized map performance to reduce ANRs and memory consumption. Zoom in to see satellite labels.
     </string>
 
     <!-- AMSAT Status screen -->
diff --git a/fastlane/metadata/android/en-US/changelogs/default.txt b/fastlane/metadata/android/en-US/changelogs/default.txt
index 88bd5615..259eeef9 100644
--- a/fastlane/metadata/android/en-US/changelogs/default.txt
+++ b/fastlane/metadata/android/en-US/changelogs/default.txt
@@ -1,7 +1,5 @@
-* Added AMSAT status tracking page by MCKero6423 (#234)
-* Tweaked Radar track on reposition by atsunatsu (#235)
-* Tweaked linear transponder calc by atsunatsu (#236)
-* Added saving per-sat doppler offset by atsunatsu (#237)
-* Added custom freq offset setting to network reporting
-* Added ability to customize data sources via import
-* Fixed star chart in README by PingouinFerreux (#240)
+* Tweaked sun calculations, added tests by atsunatsu (#241)
+* Overhauled sources import, added HTTP status by wty2019wty (#242)
+* Localized AMSAT status screen for Chinese by atsunatsu (#245)
+* Extracted hardcoded UI strings to resources by TianhengZhuang (#247)
+* Added AMSAT satellite status reports submission by atsunatsu (#248)
diff --git a/feature/map/src/main/java/com/rtbishop/look4sat/feature/map/MapNightOverlay.kt b/feature/map/src/main/java/com/rtbishop/look4sat/feature/map/MapNightOverlay.kt
index db31dfc1..33e17381 100644
--- a/feature/map/src/main/java/com/rtbishop/look4sat/feature/map/MapNightOverlay.kt
+++ b/feature/map/src/main/java/com/rtbishop/look4sat/feature/map/MapNightOverlay.kt
@@ -21,6 +21,7 @@ import android.graphics.Canvas
 import android.graphics.Color
 import android.graphics.Paint
 import android.graphics.RectF
+import org.osmdroid.util.GeoPoint
 import org.osmdroid.views.MapView
 import org.osmdroid.views.overlay.Overlay
 import kotlin.math.cos
@@ -39,9 +40,11 @@ import kotlin.math.sin
  * exceeds 90°, i.e. the dot product of the two unit vectors is negative:
  *   dot = sin(lat)*sin(sunLat) + cos(lat)*cos(sunLat)*cos(lon - sunLon) < 0
  *
- * Performance: we sample one column per [stepPx] pixels (default 4) and draw
+ * Performance: we sample one column per stepPx pixels (default 4) and draw
  * filled vertical rectangles.  On a 1080-wide screen this means ~270 trig
- * evaluations per row, which is imperceptible.
+ * evaluations per row, which is imperceptible.  draw() is called on every
+ * frame, so it must stay allocation-free — all fromPixels() calls reuse a
+ * single GeoPoint instance.
  */
 class MapNightOverlay : Overlay() {
 
@@ -58,6 +61,9 @@ class MapNightOverlay : Overlay() {
 
     private val rect = RectF()
 
+    /** Reused across every fromPixels() call — draw() runs on every frame, so it must not allocate */
+    private val reusableGeoPoint = GeoPoint(0.0, 0.0)
+
     override fun draw(canvas: Canvas, mapView: MapView, shadow: Boolean) {
         if (shadow) return
 
@@ -71,6 +77,15 @@ class MapNightOverlay : Overlay() {
         val h = mapView.height
         val stepPx = 4 // sample every N pixels — balance quality vs CPU
 
+        // The map is never rotated, so latitude depends only on y and longitude only on x.
+        // Resolve the top/bottom latitudes once instead of once per column.
+        val latTopRad = Math.toRadians((proj.fromPixels(0, 0, reusableGeoPoint) ?: return).latitude)
+        val latBotRad = Math.toRadians((proj.fromPixels(0, h - 1, reusableGeoPoint) ?: return).latitude)
+        val sinLatTop = sin(latTopRad)
+        val cosLatTop = cos(latTopRad)
+        val sinLatBot = sin(latBotRad)
+        val cosLatBot = cos(latBotRad)
+
         // We scan column by column. For each column we determine the longitude,
         // then find the latitude range that is in night and shade it.
         // Since longitude is constant along a vertical strip and the day/night
@@ -79,22 +94,14 @@ class MapNightOverlay : Overlay() {
 
         var x = 0
         while (x < w) {
-            // Get the geographic coordinate at the top and bottom of this column.
-            val geoTop = proj.fromPixels(x, 0) ?: run { x += stepPx; continue }
-            val geoBot = proj.fromPixels(x, h - 1) ?: run { x += stepPx; continue }
-
+            val geoTop = proj.fromPixels(x, 0, reusableGeoPoint) ?: run { x += stepPx; continue }
             val lonRad = Math.toRadians(geoTop.longitude)
             val cosLonDiff = cos(lonRad - sunLonRad)
 
-            // Top pixel geographic lat
-            val latTopRad = Math.toRadians(geoTop.latitude)
-            // Bottom pixel geographic lat (osmdroid: y=0 is top of screen, higher y = lower lat)
-            val latBotRad = Math.toRadians(geoBot.latitude)
-
             // dot(sunVec, pointVec) < 0 → night
             // dot = sin(lat)*sinSunLat + cos(lat)*cosSunLat*cosLonDiff
-            val dotTop = sin(latTopRad) * sinSunLat + cos(latTopRad) * cosSunLat * cosLonDiff
-            val dotBot = sin(latBotRad) * sinSunLat + cos(latBotRad) * cosSunLat * cosLonDiff
+            val dotTop = sinLatTop * sinSunLat + cosLatTop * cosSunLat * cosLonDiff
+            val dotBot = sinLatBot * sinSunLat + cosLatBot * cosSunLat * cosLonDiff
 
             when {
                 dotTop < 0 && dotBot < 0 -> {
@@ -142,7 +149,7 @@ class MapNightOverlay : Overlay() {
         var hi = yBot
         while (hi - lo > 1) {
             val mid = (lo + hi) / 2
-            val geo = proj.fromPixels(x, mid) ?: return mid
+            val geo = proj.fromPixels(x, mid, reusableGeoPoint) ?: return mid
             val latRad = Math.toRadians(geo.latitude)
             val dot = sin(latRad) * sinSunLat + cos(latRad) * cosSunLat * cosLonDiff
             if (dot < 0) hi = mid else lo = mid
diff --git a/feature/map/src/main/java/com/rtbishop/look4sat/feature/map/MapScreen.kt b/feature/map/src/main/java/com/rtbishop/look4sat/feature/map/MapScreen.kt
index 3ed234d4..fec5a37d 100644
--- a/feature/map/src/main/java/com/rtbishop/look4sat/feature/map/MapScreen.kt
+++ b/feature/map/src/main/java/com/rtbishop/look4sat/feature/map/MapScreen.kt
@@ -62,7 +62,6 @@ import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import androidx.lifecycle.viewmodel.compose.viewModel
 import com.rtbishop.look4sat.core.domain.predict.GeoPos
 import com.rtbishop.look4sat.core.domain.predict.OrbitalObject
-import com.rtbishop.look4sat.core.domain.predict.OrbitalPos
 import com.rtbishop.look4sat.core.domain.repository.IContainerProvider
 import com.rtbishop.look4sat.core.presentation.IconCard
 import com.rtbishop.look4sat.core.presentation.NextPassRow
@@ -71,6 +70,10 @@ import com.rtbishop.look4sat.core.presentation.TimerRow
 import com.rtbishop.look4sat.core.presentation.TopBar
 import com.rtbishop.look4sat.core.presentation.isVerticalLayout
 import com.rtbishop.look4sat.core.presentation.layoutPadding
+import org.osmdroid.events.DelayedMapListener
+import org.osmdroid.events.MapListener
+import org.osmdroid.events.ScrollEvent
+import org.osmdroid.events.ZoomEvent
 import org.osmdroid.tileprovider.tilesource.XYTileSource
 import org.osmdroid.util.GeoPoint
 import org.osmdroid.views.CustomZoomButtonsController
@@ -126,6 +129,21 @@ fun MapDestination() {
     val viewModel: MapViewModel = viewModel(factory = MapViewModel.factory(container))
     val uiState by viewModel.uiState.collectAsStateWithLifecycle()
     val mapView = rememberMapViewWithLifecycle()
+    val lifecycle = LocalLifecycleOwner.current.lifecycle
+    DisposableEffect(lifecycle) {
+        val observer = LifecycleEventObserver { _, event ->
+            when (event) {
+                Lifecycle.Event.ON_START -> viewModel.onAction(MapAction.SetVisible(true))
+                Lifecycle.Event.ON_STOP -> viewModel.onAction(MapAction.SetVisible(false))
+                else -> {}
+            }
+        }
+        lifecycle.addObserver(observer)
+        onDispose {
+            lifecycle.removeObserver(observer)
+            viewModel.onAction(MapAction.SetVisible(false))
+        }
+    }
     MapScreen(uiState, viewModel::onAction, mapView)
 }
 
@@ -283,19 +301,49 @@ private fun setStationPosition(stationPos: GeoPos, mapView: MapView) {
 private val markerPool = HashMap<String, Marker>()
 private var lastMapView: MapView? = null
 
+/**
+ * Above this many satellites inside the viewport labels are dropped in favor of a single
+ * shared dot icon. Per-satellite label bitmaps cost ~90KB each, so drawing thousands of them
+ * exhausts memory and stalls the UI thread — and overlapping labels are unreadable anyway.
+ */
+private const val LABEL_LIMIT = 128
+
+/** Degrees of space around the viewport so markers don't pop in at the edges */
+private const val VIEWPORT_MARGIN = 8.0
+
+/** Debounce for viewport-driven marker refreshes, in milliseconds */
+private const val MAP_LISTENER_DELAY = 128L
+
+/** Shared dot icon used when too many satellites are visible to label them */
+private var dotIcon: Drawable? = null
+
+/** Scratch list reused every frame to avoid per-tick allocation */
+private val visibleSats = ArrayList<Pair<OrbitalObject, GeoPos>>()
+
+/** Last emitted positions, replayed on scroll/zoom so culled markers appear without waiting for a tick */
+private var lastPositions: Map<OrbitalObject, GeoPos>? = null
+private var lastAction: ((OrbitalObject) -> Unit)? = null
+
 private fun setPositions(
     posMap: Map<OrbitalObject, GeoPos>,
     mapView: MapView,
     action: (OrbitalObject) -> Unit
 ) {
     try {
+        lastPositions = posMap
+        lastAction = action
         // Clear caches when the MapView instance changes (e.g. config change)
         if (lastMapView !== mapView) {
             lastMapView = mapView
             markerPool.clear()
             iconCache.evictAll()
+            dotIcon = null
             footprintPolyline = null
             footprintPoints = null
+            mapView.addMapListener(DelayedMapListener(object : MapListener {
+                override fun onScroll(event: ScrollEvent?) = refreshPositions(mapView)
+                override fun onZoom(event: ZoomEvent?) = refreshPositions(mapView)
+            }, MAP_LISTENER_DELAY))
         }
         // Reuse the existing FolderOverlay — creating a new one and replacing it
         // causes osmdroid to detach shared Marker objects, making them invisible.
@@ -304,17 +352,48 @@ private fun setPositions(
         }
         folder.items.clear()
 
-        val activeNames = HashSet<String>(posMap.size)
-        posMap.forEach { (satellite, geoPos) ->
+        // Cull satellites outside the viewport: only meaningful once zoomed in, but that is
+        // exactly when marker labels are shown and drawing is most expensive.
+        visibleSats.clear()
+        if (mapView.width > 0 && mapView.height > 0) {
+            val box = mapView.boundingBox
+            val latNorth = box.latNorth + VIEWPORT_MARGIN
+            val latSouth = box.latSouth - VIEWPORT_MARGIN
+            val lonWest = box.lonWest - VIEWPORT_MARGIN
+            val lonEast = box.lonEast + VIEWPORT_MARGIN
+            val wrapsDateLine = box.lonWest > box.lonEast
+            for ((satellite, geoPos) in posMap) {
+                val lat = geoPos.latitude
+                if (lat !in latSouth..latNorth) continue
+                val lon = geoPos.longitude
+                val isLonVisible = if (wrapsDateLine) lon >= lonWest || lon <= lonEast
+                else lon in lonWest..lonEast
+                if (isLonVisible) visibleSats.add(satellite to geoPos)
+            }
+        } else {
+            for (entry in posMap) visibleSats.add(entry.key to entry.value)
+        }
+
+        val showLabels = visibleSats.size <= LABEL_LIMIT
+        val activeNames = HashSet<String>(visibleSats.size)
+        for ((satellite, geoPos) in visibleSats) {
             val name = satellite.data.name
             activeNames.add(name)
             val marker = markerPool.getOrPut(name) {
                 Marker(mapView).apply {
                     setInfoWindow(null)
                     setAnchor(Marker.ANCHOR_CENTER, Marker.ANCHOR_CENTER)
-                    icon = getCachedTextIcon(name, mapView)
+                    // Resolve the satellite via relatedObject so the listener is allocated
+                    // once per marker instead of once per satellite per tick
+                    setOnMarkerClickListener { clicked, _ ->
+                        (clicked.relatedObject as? OrbitalObject)?.let(action)
+                        true
+                    }
                 }
             }
+            marker.relatedObject = satellite
+            val icon = if (showLabels) getCachedTextIcon(name, mapView) else getDotIcon(mapView)
+            if (marker.icon !== icon) marker.icon = icon
             // Update position in-place — reuse existing GeoPoint if available
             val pos = marker.position
             if (pos != null) {
@@ -323,22 +402,32 @@ private fun setPositions(
             } else {
                 marker.position = GeoPoint(geoPos.latitude, geoPos.longitude)
             }
-            marker.setOnMarkerClickListener { _, _ ->
-                action(satellite)
-                true
-            }
             folder.add(marker)
         }
-        // Evict markers for satellites no longer tracked
-        val iter = markerPool.keys.iterator()
-        while (iter.hasNext()) {
-            if (iter.next() !in activeNames) iter.remove()
-        }
+        // Evict markers that are no longer tracked or no longer visible
+        markerPool.keys.retainAll(activeNames)
+        visibleSats.clear()
     } catch (e: Exception) {
         println(e)
     }
 }
 
+/** Re-applies the last known positions against the new viewport after a pan or zoom */
+private fun refreshPositions(mapView: MapView): Boolean {
+    val posMap = lastPositions ?: return false
+    val action = lastAction ?: return false
+    setPositions(posMap, mapView, action)
+    mapView.invalidate()
+    return true
+}
+
+private fun getDotIcon(mapView: MapView): Drawable = dotIcon ?: run {
+    val size = 20
+    val bitmap = createBitmap(size, size)
+    Canvas(bitmap).drawCircle(size / 2f, size / 2f, size / 2f - 2f, textPaint)
+    bitmap.toDrawable(mapView.context.resources).also { dotIcon = it }
+}
+
 private fun getCachedTextIcon(name: String, mapView: MapView): Drawable {
     iconCache[name]?.let { return it }
     val labelRect = Rect()
@@ -376,9 +465,8 @@ private fun setSatelliteTrack(satTrack: List<List<GeoPos>>, mapView: MapView) {
 private var footprintPolyline: Polyline? = null
 private var footprintPoints: ArrayList<GeoPoint>? = null
 
-private fun setFootprint(orbitalPos: OrbitalPos, mapView: MapView) {
+private fun setFootprint(rangeCircle: List<GeoPos>, mapView: MapView) {
     try {
-        val rangeCircle = orbitalPos.getRangeCircle()
         var pts = footprintPoints
         if (pts == null || pts.size != rangeCircle.size) {
             pts = ArrayList(rangeCircle.size)
@@ -508,9 +596,28 @@ private fun rememberMapViewWithLifecycle(): MapView {
         lifecycle.addObserver(lifecycleObserver)
         onDispose { lifecycle.removeObserver(lifecycleObserver) }
     }
+    // The overlay caches below are file-level (shared across MapView instances), so they must be
+    // released with the MapView or they keep the Activity and its bitmaps alive after disposal.
+    DisposableEffect(mapView) {
+        onDispose {
+            clearMapCaches()
+            mapView.onDetach()
+        }
+    }
     return mapView
 }
 
+private fun clearMapCaches() {
+    markerPool.clear()
+    iconCache.evictAll()
+    dotIcon = null
+    footprintPolyline = null
+    footprintPoints = null
+    lastPositions = null
+    lastAction = null
+    lastMapView = null
+}
+
 @Composable
 private fun rememberMapViewLifecycleObserver(mapView: MapView) = remember(mapView) {
     LifecycleEventObserver { _, event ->
diff --git a/feature/map/src/main/java/com/rtbishop/look4sat/feature/map/MapState.kt b/feature/map/src/main/java/com/rtbishop/look4sat/feature/map/MapState.kt
index e1274618..7664c3e0 100644
--- a/feature/map/src/main/java/com/rtbishop/look4sat/feature/map/MapState.kt
+++ b/feature/map/src/main/java/com/rtbishop/look4sat/feature/map/MapState.kt
@@ -20,7 +20,6 @@ package com.rtbishop.look4sat.feature.map
 import com.rtbishop.look4sat.core.domain.predict.GeoPos
 import com.rtbishop.look4sat.core.domain.predict.OrbitalObject
 import com.rtbishop.look4sat.core.domain.predict.OrbitalPass
-import com.rtbishop.look4sat.core.domain.predict.OrbitalPos
 
 data class MapState(
     val mapData: MapData? = null,
@@ -29,7 +28,7 @@ data class MapState(
     val stationPosition: GeoPos? = null,
     val orbitalPass: OrbitalPass,
     val track: List<List<GeoPos>>? = null,
-    val footprint: OrbitalPos? = null,
+    val footprint: List<GeoPos>? = null,
     val positions: Map<OrbitalObject, GeoPos>? = null,
     val sunLatDeg: Double = 0.0,
     val sunLonDeg: Double = 0.0,
@@ -42,6 +41,7 @@ sealed interface MapAction {
     data object SelectNext : MapAction
     data class SelectItem(val item: OrbitalObject) : MapAction
     data class SelectDefaultItem(val catnum: Int) : MapAction
+    data class SetVisible(val isVisible: Boolean) : MapAction
 }
 
 data class MapData(
diff --git a/feature/map/src/main/java/com/rtbishop/look4sat/feature/map/MapViewModel.kt b/feature/map/src/main/java/com/rtbishop/look4sat/feature/map/MapViewModel.kt
index 118a089d..59407aa4 100644
--- a/feature/map/src/main/java/com/rtbishop/look4sat/feature/map/MapViewModel.kt
+++ b/feature/map/src/main/java/com/rtbishop/look4sat/feature/map/MapViewModel.kt
@@ -36,6 +36,7 @@ import com.rtbishop.look4sat.core.domain.utility.toMapGeoPos
 import com.rtbishop.look4sat.core.domain.utility.toDegrees
 import com.rtbishop.look4sat.core.domain.utility.toTimerString
 import com.rtbishop.look4sat.core.presentation.getDefaultPass
+import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.Job
 import kotlinx.coroutines.async
 import kotlinx.coroutines.awaitAll
@@ -45,10 +46,12 @@ import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.collectLatest
+import kotlinx.coroutines.flow.first
 import kotlinx.coroutines.flow.update
 import kotlinx.coroutines.isActive
 import kotlinx.coroutines.launch
 import java.util.Date
+import kotlin.time.Duration.Companion.milliseconds
 
 class MapViewModel(
     private val satelliteRepo: ISatelliteRepo,
@@ -69,6 +72,9 @@ class MapViewModel(
     private var dataUpdateJob: Job? = null
     private var dataUpdateRate = 1000L
     private var selectedOrbitalObject: OrbitalObject? = null
+
+    /** Gates the prediction loop so it doesn't burn CPU while the map isn't on screen */
+    private val isScreenVisible = MutableStateFlow(true)
     val uiState: StateFlow<MapState> = _uiState
 
     init {
@@ -87,6 +93,7 @@ class MapViewModel(
             MapAction.SelectNext -> scrollSelection(false)
             is MapAction.SelectItem -> selectSatellite(action.item)
             is MapAction.SelectDefaultItem -> selectDefaultSatellite(action.catnum)
+            is MapAction.SetVisible -> isScreenVisible.value = action.isVisible
         }
     }
 
@@ -124,7 +131,11 @@ class MapViewModel(
         selectedOrbitalObject = orbitalObject
         viewModelScope.launch {
             dataUpdateJob?.cancelAndJoin()
-            dataUpdateJob = launch {
+            // Default dispatcher is mandatory: viewModelScope is Main.immediate, and every
+            // satelliteRepo call internally hops to Default and resumes back on the caller's
+            // dispatcher. On Main that posts one continuation per satellite per tick, which
+            // floods the looper and ANRs for users tracking thousands of objects.
+            dataUpdateJob = launch(Dispatchers.Default) {
                 val dateNow = Date()
                 getStationPosition()
                 getSatTrack(orbitalObject, stationPos, dateNow)
@@ -135,9 +146,11 @@ class MapViewModel(
                     else -> updateFreq
                 }
                 while (isActive) {
+                    // Suspends while the map is off-screen instead of predicting into the void
+                    isScreenVisible.first { it }
                     dateNow.time = System.currentTimeMillis()
                     updateMapState(orbitalObject, allSatellites, stationPos, dateNow)
-                    delay(effectiveRate)
+                    delay(effectiveRate.milliseconds)
                 }
             }
         }
@@ -187,7 +200,8 @@ class MapViewModel(
 
         // 2. Derive footprint, info data, sun and moon position from already-computed state
         val satPos = selectedSatPos ?: satelliteRepo.getPosition(selected, pos, date.time)
-        val footprint = satPos
+        // Range circle is 721 trig-heavy points — keep it on this background dispatcher
+        val footprint = satPos.getRangeCircle()
         val mapData = buildMapData(selected, satPos, date)
         val sunPos = CelestialComputer.getSunPosition(stationPos, date.time)
         val moonPos = CelestialComputer.getMoonPosition(stationPos, date.time)
@@ -294,7 +308,7 @@ class MapViewModel(
 
     companion object {
         /** Number of parallel chunks for satellite position computation */
-        private const val PARALLEL_CHUNKS = 4
+        private val PARALLEL_CHUNKS = Runtime.getRuntime().availableProcessors().coerceIn(2, 8)
 
         fun factory(container: IMainContainer) = viewModelFactory {
             initializer {