diff --git a/Rewrite.vcxproj b/Rewrite.vcxproj
index 998bf96..26657a3 100644
--- a/Rewrite.vcxproj
+++ b/Rewrite.vcxproj
@@ -78,12 +78,14 @@
     <ClCompile Include="Globals.cpp" />
     <ClCompile Include="Julian.cpp" />
     <ClCompile Include="main.cpp" />
+    <ClCompile Include="Tle.cpp" />
     <ClCompile Include="Vector.cpp" />
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="Coord.h" />
     <ClInclude Include="Globals.h" />
     <ClInclude Include="Julian.h" />
+    <ClInclude Include="Tle.h" />
     <ClInclude Include="Vector.h" />
   </ItemGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
diff --git a/Rewrite.vcxproj.filters b/Rewrite.vcxproj.filters
index 7e3811e..0d3971e 100644
--- a/Rewrite.vcxproj.filters
+++ b/Rewrite.vcxproj.filters
@@ -30,6 +30,9 @@
     <ClCompile Include="main.cpp">
       <Filter>Source Files</Filter>
     </ClCompile>
+    <ClCompile Include="Tle.cpp">
+      <Filter>Source Files</Filter>
+    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="Coord.h">
@@ -44,5 +47,8 @@
     <ClInclude Include="Globals.h">
       <Filter>Header Files</Filter>
     </ClInclude>
+    <ClInclude Include="Tle.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
   </ItemGroup>
 </Project>
\ No newline at end of file
diff --git a/Tle.cpp b/Tle.cpp
new file mode 100644
index 0000000..9abccf2
--- /dev/null
+++ b/Tle.cpp
@@ -0,0 +1,289 @@
+#include "Tle.h"
+
+#include <cassert>
+#include <cstdlib>
+
+Tle::Tle(const std::string& name, const std::string& line_one, const std::string& line_two) {
+    name_ = name;
+    line_one_ = line_one;
+    line_two_ = line_two;
+
+    Initialize();
+}
+
+Tle::Tle(const Tle& tle) {
+    name_ = tle.name_;
+    line_one_ = tle.line_one_;
+    line_two_ = tle.line_two_;
+    date_ = tle.date_;
+
+    for (int fld = FLD_FIRST; fld < FLD_LAST; fld++) {
+        fields_[fld] = tle.fields_[fld];
+    }
+}
+
+Tle::~Tle() {
+}
+
+double Tle::GetField(TleField fld, TleUnits units) const {
+    assert((FLD_FIRST <= fld) && (fld < FLD_LAST));
+    assert((U_FIRST <= units) && (units < U_LAST));
+
+    double value = fields_[fld].second;
+    double converted = 0.0;
+
+    switch (fld) {
+        case FLD_I:
+        case FLD_RAAN:
+        case FLD_ARGPER:
+        case FLD_M:
+        {
+            /*
+             * native format is degrees
+             */
+            if (units == U_RAD)
+                converted = Globals::Deg2Rad(value);
+            break;
+        }
+        default:
+        {
+            converted = value;
+            break;
+        }
+    }
+
+    return converted;
+}
+
+/*
+ * get field represented as a string
+ */
+std::string Tle::GetFieldString(TleField fld, bool append_units) const {
+    assert((FLD_FIRST <= fld) && (fld < FLD_LAST));
+
+    std::string str = fields_[fld].first;
+
+    if (append_units)
+        str += GetUnits(fld);
+
+    return str;
+}
+
+/*
+ * get the units for a field
+ */
+std::string Tle::GetUnits(TleField field) const {
+    static const std::string strDegrees = " degrees";
+    static const std::string strRevsPerDay = " revs / day";
+    static const std::string strNull = "";
+
+    switch (field) {
+        case FLD_I:
+        case FLD_RAAN:
+        case FLD_ARGPER:
+        case FLD_M:
+            return strDegrees;
+
+        case FLD_MMOTION:
+            return strRevsPerDay;
+
+        default:
+            return strNull;
+    }
+}
+
+/*
+ * convert a raw string into an exponent string
+ */
+std::string Tle::ExpToDecimal(const std::string& str) {
+    static const int kColumnSign = 0;
+    static const int kLengthSign = 1;
+    static const int kColumnMantissa = 1;
+    static const int kLengthMantissa = 5;
+    static const int kColumnExp = 6;
+    static const int kLengthExp = 2;
+
+    assert(8 == str.length());
+
+    std::string value;
+    value = str.substr(kColumnSign, kLengthSign);
+    value += ".";
+    value += str.substr(kColumnMantissa, kLengthMantissa);
+    value += "e";
+    value += str.substr(kColumnExp, kLengthExp);
+
+    return value;
+}
+
+/*
+ * extract all variables
+ */
+void Tle::Initialize() {
+    assert(!name_.empty());
+    assert(!line_one_.empty());
+    assert(!line_two_.empty());
+
+    /*
+     * line 1
+     */
+
+    fields_[FLD_NORADNUM].first = line_one_.substr(TLE1_COL_SATNUM, TLE1_LEN_SATNUM);
+    fields_[FLD_INTLDESC].first = line_one_.substr(TLE1_COL_INTLDESC_A, TLE1_LEN_INTLDESC_A +
+            TLE1_LEN_INTLDESC_B + TLE1_LEN_INTLDESC_C);
+    fields_[FLD_EPOCHYEAR].first = line_one_.substr(TLE1_COL_EPOCH_A, TLE1_LEN_EPOCH_A);
+
+    fields_[FLD_EPOCHDAY].first = line_one_.substr(TLE1_COL_EPOCH_B, TLE1_LEN_EPOCH_B);
+
+    if (line_one_[TLE1_COL_MEANMOTIONDT] == '-') {
+        // value is negative
+        fields_[FLD_MMOTIONDT].first = "-0";
+    } else
+        fields_[FLD_MMOTIONDT].first = "0";
+
+    fields_[FLD_MMOTIONDT].first += line_one_.substr(TLE1_COL_MEANMOTIONDT + 1, TLE1_LEN_MEANMOTIONDT);
+
+    // decimal point assumed; exponential notation
+    fields_[FLD_MMOTIONDT2].first = ExpToDecimal(line_one_.substr(TLE1_COL_MEANMOTIONDT2, TLE1_LEN_MEANMOTIONDT2));
+
+    // decimal point assumed; exponential notation
+    fields_[FLD_BSTAR].first = ExpToDecimal(line_one_.substr(TLE1_COL_BSTAR, TLE1_LEN_BSTAR));
+
+    fields_[FLD_SET].first = line_one_.substr(TLE1_COL_ELNUM, TLE1_LEN_ELNUM);
+    TrimLeft(fields_[FLD_SET].first);
+
+    /*
+     * line 2
+     */
+
+    fields_[FLD_I].first = line_two_.substr(TLE2_COL_INCLINATION, TLE2_LEN_INCLINATION);
+    TrimLeft(fields_[FLD_I].first);
+
+    fields_[FLD_RAAN].first = line_two_.substr(TLE2_COL_RAASCENDNODE, TLE2_LEN_RAASCENDNODE);
+    TrimLeft(fields_[FLD_RAAN].first);
+
+    // decimal point is assumed
+    fields_[FLD_E].first = "0.";
+    fields_[FLD_E].first += line_two_.substr(TLE2_COL_ECCENTRICITY, TLE2_LEN_ECCENTRICITY);
+
+    fields_[FLD_ARGPER].first = line_two_.substr(TLE2_COL_ARGPERIGEE, TLE2_LEN_ARGPERIGEE);
+    TrimLeft(fields_[FLD_ARGPER].first);
+
+    fields_[FLD_M].first = line_two_.substr(TLE2_COL_MEANANOMALY, TLE2_LEN_MEANANOMALY);
+    TrimLeft(fields_[FLD_M].first);
+
+    fields_[FLD_MMOTION].first = line_two_.substr(TLE2_COL_MEANMOTION, TLE2_LEN_MEANMOTION);
+    TrimLeft(fields_[FLD_MMOTION].first);
+
+    fields_[FLD_ORBITNUM].first = line_two_.substr(TLE2_COL_REVATEPOCH, TLE2_LEN_REVATEPOCH);
+    TrimLeft(fields_[FLD_ORBITNUM].first);
+
+    // update double variables
+    for (int fld = FLD_FIRST; fld < FLD_LAST; fld++) {
+        fields_[fld].second = atof(fields_[fld].first.c_str());
+    }
+
+    int epochYear = (int) GetField(Tle::FLD_EPOCHYEAR);
+    double epochDay = GetField(Tle::FLD_EPOCHDAY);
+
+    if (epochYear < 57)
+        epochYear += 2000;
+    else
+        epochYear += 1900;
+
+    date_ = Julian(epochYear, epochDay);
+}
+
+/*
+ * validate a line
+ */
+bool Tle::IsValidLine(std::string& str, TleLine line) {
+    TrimLeft(str);
+    TrimRight(str);
+
+    const std::string line1_validation = "1 NNNNNC NNNNAAAA NNNNN.NNNNNNNN +.NNNNNNNN +NNNNN-N +NNNNN-N N NNNNN";
+    const std::string line2_validation = "2 NNNNN NNN.NNNN NNN.NNNN NNNNNNN NNN.NNNN NNN.NNNN NN.NNNNNNNNNNNNNN";
+
+    if (Tle::LINE_ONE == line) {
+        if (!ValidateLine(line1_validation, str))
+            return false;
+    } else if (Tle::LINE_TWO == line) {
+        if (!ValidateLine(line2_validation, str))
+            return false;
+    }
+
+    // Last char in string must be checksum
+    // int chk = CheckSum(str);
+    // if (chk != (str[TLE_LEN_LINE_DATA - 1] - '0'))
+    //   return false;
+
+    return true;
+}
+
+/*
+ * validate line given a pattern
+ */
+bool Tle::ValidateLine(const std::string& pattern, const std::string& line) {
+    assert(pattern.length() == line.length());
+
+    std::string::size_type pos = 0;
+
+    while (pos != line.length() - 1) {
+        if (isdigit(pattern[pos]) || pattern[pos] == ' ' || pattern[pos] == '.') {
+            if (pattern[pos] != line[pos])
+                return false;
+        } else if (pattern[pos] == 'N') {
+            if (!isdigit(line[pos]) && line[pos] != ' ')
+                return false;
+        }
+        pos++;
+    }
+
+    return true;
+}
+
+/*
+ * compute checksum
+ */
+int Tle::CheckSum(const std::string& str) {
+    size_t len = str.size() - 1;
+    int xsum = 0;
+
+    for (size_t i = 0; i < len; i++) {
+        char ch = str[i];
+        if (isdigit(ch))
+            xsum += (ch - '0');
+        else if (ch == '-')
+            xsum++;
+    }
+
+    return (xsum % 10);
+}
+
+/*
+ * trim left of string
+ */
+void Tle::TrimLeft(std::string& s) {
+    if (!s.empty()) {
+        std::string::size_type pos = s.find_first_not_of(' ');
+
+        if (pos != std::string::npos)
+            s.erase(0, pos);
+        else
+            s.clear();
+    }
+}
+
+/*
+ * trim right of string
+ */
+void Tle::TrimRight(std::string& s) {
+    if (!s.empty()) {
+        std::string::size_type pos = s.find_last_not_of(' ');
+
+        if (pos != std::string::npos)
+            s.erase(pos + 1);
+        else
+            s.clear();
+    }
+}
+
diff --git a/Tle.h b/Tle.h
new file mode 100644
index 0000000..e5b41d2
--- /dev/null
+++ b/Tle.h
@@ -0,0 +1,182 @@
+#ifndef TLE_H_
+#define TLE_H_
+
+#include "Globals.h"
+#include "Julian.h"
+
+#include <iostream>
+
+class Tle {
+public:
+    Tle(const std::string& name, const std::string& line_one, const std::string& line_two);
+    Tle(const Tle& tle);
+    virtual ~Tle();
+
+    enum TleLine {
+        LINE_ZERO,
+        LINE_ONE,
+        LINE_TWO
+    };
+
+    enum TleField {
+        FLD_FIRST,
+        FLD_NORADNUM = FLD_FIRST,
+        FLD_INTLDESC,
+        FLD_SET, // Tle set number
+        FLD_EPOCHYEAR, // Epoch: Last two digits of year
+        FLD_EPOCHDAY, // Epoch: Fractional Julian Day of year
+        FLD_ORBITNUM, // Orbit at epoch
+        FLD_I, // Inclination
+        FLD_RAAN, // R.A. ascending node
+        FLD_E, // Eccentricity
+        FLD_ARGPER, // Argument of perigee
+        FLD_M, // Mean anomaly
+        FLD_MMOTION, // Mean motion
+        FLD_MMOTIONDT, // First time derivative of mean motion
+        FLD_MMOTIONDT2, // Second time derivative of mean motion
+        FLD_BSTAR, // BSTAR Drag
+        FLD_LAST // MUST be last
+    };
+
+    enum TleUnits {
+        U_FIRST,
+        U_RAD = U_FIRST, // radians
+        U_DEG, // degrees
+        U_NATIVE, // Tle format native units (no conversion)
+        U_LAST // MUST be last
+    };
+
+    /*
+     * initialize from raw tle strings
+     */
+    void Initialize();
+
+    /*
+     * get field represented as a double
+     */
+    double GetField(TleField fld, TleUnits unit = U_NATIVE) const;
+    /*
+     * get field represented as a string
+     */
+    std::string GetFieldString(TleField fld, bool append_units) const;
+
+    /*
+     * get epoch of tle
+     */
+    Julian GetEpoch() const {
+        return date_;
+    }
+
+    /*
+     * compute checksum
+     */
+    static int CheckSum(const std::string& str);
+    static bool IsValidLine(std::string& str, TleLine line);
+    static void TrimLeft(std::string& str);
+    static void TrimRight(std::string& str);
+
+    std::string GetName() const {
+        return name_;
+    }
+
+    std::string GetLine1() const {
+        return line_one_;
+    }
+
+    std::string GetLine2() const {
+        return line_two_;
+    }
+
+    double GetNoradNumber() const {
+        return GetField(Tle::FLD_NORADNUM);
+    }
+
+private:
+    /*
+     * get units for a field
+     */
+    std::string GetUnits(TleField field) const;
+    /*
+     * get raw value for a field
+     */
+    double GetFieldNumeric(TleField) const;
+    /*
+     * convert a raw string into an exponent string
+     */
+    static std::string ExpToDecimal(const std::string&);
+    /*
+     * validate a line
+     */
+    static bool ValidateLine(const std::string& pattern, const std::string& line);
+
+    /*
+     * raw tle data
+     */
+    std::string name_;
+    std::string line_one_;
+    std::string line_two_;
+
+    /*
+     * epoch of tle
+     */
+    Julian date_;
+
+    // array of tle values in native string and double form
+    std::pair<std::string, double> fields_[FLD_LAST];
+
+    /*
+     * name line
+     */
+    static const unsigned int TLE_LEN_LINE_DATA = 69;
+    static const unsigned int TLE_LEN_LINE_NAME = 22;
+
+    /*
+     * line 1
+     */
+    static const unsigned int TLE1_COL_SATNUM = 2;
+    static const unsigned int TLE1_LEN_SATNUM = 5;
+    static const unsigned int TLE1_COL_INTLDESC_A = 9;
+    static const unsigned int TLE1_LEN_INTLDESC_A = 2;
+    static const unsigned int TLE1_COL_INTLDESC_B = 11;
+    static const unsigned int TLE1_LEN_INTLDESC_B = 3;
+    static const unsigned int TLE1_COL_INTLDESC_C = 14;
+    static const unsigned int TLE1_LEN_INTLDESC_C = 3;
+    static const unsigned int TLE1_COL_EPOCH_A = 18;
+    static const unsigned int TLE1_LEN_EPOCH_A = 2;
+    static const unsigned int TLE1_COL_EPOCH_B = 20;
+    static const unsigned int TLE1_LEN_EPOCH_B = 12;
+    static const unsigned int TLE1_COL_MEANMOTIONDT = 33;
+    static const unsigned int TLE1_LEN_MEANMOTIONDT = 10;
+    static const unsigned int TLE1_COL_MEANMOTIONDT2 = 44;
+    static const unsigned int TLE1_LEN_MEANMOTIONDT2 = 8;
+    static const unsigned int TLE1_COL_BSTAR = 53;
+    static const unsigned int TLE1_LEN_BSTAR = 8;
+    static const unsigned int TLE1_COL_EPHEMTYPE = 62;
+    static const unsigned int TLE1_LEN_EPHEMTYPE = 1;
+    static const unsigned int TLE1_COL_ELNUM = 64;
+    static const unsigned int TLE1_LEN_ELNUM = 4;
+
+    /*
+     * line 2
+     */
+    static const unsigned int TLE2_COL_SATNUM = 2;
+    static const unsigned int TLE2_LEN_SATNUM = 5;
+    static const unsigned int TLE2_COL_INCLINATION = 8;
+    static const unsigned int TLE2_LEN_INCLINATION = 8;
+    static const unsigned int TLE2_COL_RAASCENDNODE = 17;
+    static const unsigned int TLE2_LEN_RAASCENDNODE = 8;
+    static const unsigned int TLE2_COL_ECCENTRICITY = 26;
+    static const unsigned int TLE2_LEN_ECCENTRICITY = 7;
+    static const unsigned int TLE2_COL_ARGPERIGEE = 34;
+    static const unsigned int TLE2_LEN_ARGPERIGEE = 8;
+    static const unsigned int TLE2_COL_MEANANOMALY = 43;
+    static const unsigned int TLE2_LEN_MEANANOMALY = 8;
+    static const unsigned int TLE2_COL_MEANMOTION = 52;
+    static const unsigned int TLE2_LEN_MEANMOTION = 11;
+    static const unsigned int TLE2_COL_REVATEPOCH = 63;
+    static const unsigned int TLE2_LEN_REVATEPOCH = 5;
+};
+
+#endif
+
+
diff --git a/main.cpp b/main.cpp
index c91bc2a..0683211 100644
--- a/main.cpp
+++ b/main.cpp
@@ -1,4 +1,5 @@
 #include "Julian.h"
+#include "Tle.h"
 
 #include <stdio.h>