NVS-02 is a second-generation navigation satellite of the Indian regional navigation satellite system NavIC. It was launched on Jan. 28, 2025, but could not reach its designated orbit due to a malfunction of a valve of the thrusters. Thus, the satellite is still in its transfer orbit. As of April 2025, the NVS-02 perigee is about 190 km, whereas the apogee is 37,400 km above the Earth’s surface. The inclination is about 21° and the eccentricity is 0.74. The groundtrack of NVS-02 is illustrated in Figure 1 and currently has a repeat cycle of about six days.
<p>As of today, starting on Feb. 19, 2025, a decent number of receivers of the International GNSS Service are tracking the L5 signal of NVS-02 with the pseudo-random noise number I11. The L5 tracking of dedicated stations on individual days is indicated by different colors in Figure 1. Although the groundtrack has global coverage, no stations in Northern and Southern America have tracked I11 so far. The tracking is limited to periods when the satellite is near the apogee with altitudes between 23,000 km and 37,400 km and visible from the Indian Ocean region. During these periods, indicated in pink in Figure 1, the transmitter is active and the antenna is roughly pointing toward Earth.</p> <p><strong>Figure 2</strong> shows the carrier-to-noise density ratio (C/N0) of the NVS-02 L5 signal tracked by a Septentrio PolaRx5 receiver at the German Space Operations Center (GSOC) of the German Aerospace Center (DLR) in Oberpfaffenhofen, Germany. Sudden drops in the C/N0 occur at about 8°, 28°, 46° and 52°. Here, the line of sight to the satellite is at the edge of the transmit antenna main lobe with a significantly lower gain, introducing the drop in signal power and, finally, the loss of lock.</p> <div class="wp-block-image"> <figure class="aligncenter size-full is-resized"><img decoding="async" width="600" height="340" src="https://www.gpsworld.com/wp-content/uploads/2025/04/GPS_web_NVS02_Figure2_600x340_04242025.webp" alt="Figure 2: Elevation-dependence of the carrier-to-noise density ratio of the NVS-02 L5 signal at Oberpfaffenhofen, Germany. (All figures provided by the authors)" class="wp-image-109858" style="width:378px;height:auto" srcset="https://www.gpsworld.com/wp-content/uploads/2025/04/GPS_web_NVS02_Figure2_600x340_04242025.webp 600w, https://www.gpsworld.com/wp-content/uploads/2025/04/GPS_web_NVS02_Figure2_600x340_04242025-300x170.webp 300w, https://www.gpsworld.com/wp-content/uploads/2025/04/GPS_web_NVS02_Figure2_600x340_04242025-245x139.webp 245w" sizes="(max-width: 600px) 100vw, 600px" /><figcaption class="wp-element-caption">Figure 2: Elevation-dependence of the carrier-to-noise density ratio of the NVS-02 L5 signal at Oberpfaffenhofen, Germany. (All figures provided by the authors)</figcaption></figure></div> <p>The spectral flux density of NVS-02 in the L5, L1 and S band is shown in <strong>Figure 3</strong>. The L-band spectra have been measured with GSOC’s 30 m high-gain antenna in Weilheim, Germany. As the feed of this antenna is limited to the L band, the S band spectrum has been recorded with a 5 m dish antenna of DLR’s Institute of Communication and Navigation.</p> <div class="wp-block-image"> <figure class="alignright size-large is-resized"><img loading="lazy" decoding="async" width="597" height="1024" src="https://www.gpsworld.com/wp-content/uploads/2025/04/GPS_web_NVS02_Figure3_600x340_04242025-597x1024.webp" alt="Figure 3: Spectral flux density of NVS-02 in the L5 (top), L1 (middle) and S-band (bottom). (All figures provided by the authors)" class="wp-image-109859" style="width:436px;height:auto" srcset="https://www.gpsworld.com/wp-content/uploads/2025/04/GPS_web_NVS02_Figure3_600x340_04242025-597x1024.webp 597w, https://www.gpsworld.com/wp-content/uploads/2025/04/GPS_web_NVS02_Figure3_600x340_04242025-175x300.webp 175w, https://www.gpsworld.com/wp-content/uploads/2025/04/GPS_web_NVS02_Figure3_600x340_04242025-122x210.webp 122w, https://www.gpsworld.com/wp-content/uploads/2025/04/GPS_web_NVS02_Figure3_600x340_04242025.webp 600w" sizes="auto, (max-width: 597px) 100vw, 597px" /><figcaption class="wp-element-caption">Figure 3: Spectral flux density of NVS-02 in the L5 (top), L1 (middle) and S band (bottom). (All figures provided by the authors)</figcaption></figure></div> <p>The peak in the L5 spectrum at the center frequency of 1176.45 MHz is related to the civil Standard Positioning Service and introduced by a Binary Phase Shift Keying (BPSK) modulation with 1 MHz bandwidth. The two broader peaks with an offset of 5 MHz from the center frequency are caused by a Binary Offset Carrier (BOC) signal of the Restricted Service with a bandwidth of 2 MHz. Sidelobes of that signal are visible at the center frequency ±15 MHz and ±25 MHz.</p> <p>For the L1 band, a Synthesized Binary Offset Carrier (SBOC) is used. It consists of two BOC signals with 1 MHz bandwidth and offsets of 1 MHz and 6 MHz, respectively. The two mainlobes of the BOC (1,1) component are visible at 1575.42±1 MHz, and the mainlobes of the BOC (6,1) component at 1569 MHz and 1581 MHz. The same type of signals, as in L5, are transmitted on the S band carrier with a center frequency of 2492.028 MHz. Due to its different location in a less remote area, compared to the 30 m antenna in Weilheim, the 5 m antenna in Oberpfaffenhofen suffers from pronounced interference with other signals in the S band; the most prominent peak can be seen at 2480 MHz, several smaller and sharper peaks over the whole frequency range shown in the lower plot of Figure 3. Possible causes of these interferences are WiFi and civilian and military radiocommunication services.</p> <p>Although NVS-02’s mean orbit height is steadily decreasing due to the atmospheric drag around the perigee, the satellite will stay in orbit for at least a decade. However, navigation signal transmission might stop at any time due to operational constraints or unfavorable conditions in the non-nominal orbit.</p> <p><p>The post <a target="_blank" rel="nofollow" href="https://www.gpsworld.com/nvs-02-navigation-signals-from-transfer-orbit/">NVS-02: Navigation signals from transfer orbit</a> first appeared on <a target="_blank" rel="nofollow" href="https://www.gpsworld.com">GPS World</a>.</p></p>
