diff --git a/app/src/main/java/com/rtbishop/look4sat/data/repository/PassesRepo.kt b/app/src/main/java/com/rtbishop/look4sat/data/repository/PassesRepo.kt
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index 00000000..26653565
--- /dev/null
+++ b/app/src/main/java/com/rtbishop/look4sat/data/repository/PassesRepo.kt
@@ -0,0 +1,78 @@
+/*
+ * Look4Sat. Amateur radio satellite tracker and pass predictor.
+ * Copyright (C) 2019-2021 Arty Bishop (bishop.arty@gmail.com)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+package com.rtbishop.look4sat.data.repository
+
+import com.github.amsacode.predict4java.Satellite
+import com.rtbishop.look4sat.data.model.Result
+import com.rtbishop.look4sat.data.model.SatPass
+import com.rtbishop.look4sat.di.DefaultDispatcher
+import com.rtbishop.look4sat.utility.getPredictor
+import kotlinx.coroutines.CoroutineDispatcher
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.withContext
+import java.util.*
+import javax.inject.Inject
+import javax.inject.Singleton
+
+@Singleton
+class PassesRepo @Inject constructor(
+    private val prefsRepo: PrefsRepo,
+    @DefaultDispatcher private val defaultDispatcher: CoroutineDispatcher
+) {
+    private val _passes = MutableStateFlow<Result<MutableList<SatPass>>>(Result.InProgress)
+    val passes: StateFlow<Result<MutableList<SatPass>>> = _passes
+
+    private var selectedSatellites = emptyList<Satellite>()
+
+    suspend fun calculatePasses(satellites: List<Satellite>) {
+        if (satellites !== selectedSatellites) {
+            withContext(defaultDispatcher) {
+                _passes.value = Result.InProgress
+                selectedSatellites = satellites
+                val refDate = Date(System.currentTimeMillis())
+                val allPasses = mutableListOf<SatPass>()
+                selectedSatellites.forEach { satellite ->
+                    allPasses.addAll(getPasses(satellite, refDate))
+                }
+                val filteredPasses = filterPasses(allPasses, refDate)
+                _passes.value = Result.Success(filteredPasses)
+            }
+        }
+    }
+
+    private fun getPasses(satellite: Satellite, refDate: Date): MutableList<SatPass> {
+        val predictor = satellite.getPredictor(prefsRepo.getStationPosition())
+        val passes = predictor.getPasses(refDate, prefsRepo.getHoursAhead(), true)
+        val passList = passes.map { SatPass(satellite.tle, predictor, it) }
+        return passList as MutableList<SatPass>
+    }
+
+    private fun filterPasses(passes: MutableList<SatPass>, refDate: Date): MutableList<SatPass> {
+        val hoursAhead = prefsRepo.getHoursAhead()
+        val dateFuture = Calendar.getInstance().apply {
+            this.time = refDate
+            this.add(Calendar.HOUR, hoursAhead)
+        }.time
+        passes.removeAll { it.pass.startTime.after(dateFuture) }
+        passes.removeAll { it.pass.endTime.before(refDate) }
+        passes.removeAll { it.pass.maxEl < prefsRepo.getMinElevation() }
+        passes.sortBy { it.pass.startTime }
+        return passes
+    }
+}
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