USNS Impeccable (T-AGOS-23)

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USNS Impeccable T-AGOS-23.jpg
USNS Impeccable
Name: USNS Impeccable
Owner: United States Navy
Operator: Military Sealift Command
Builder: American Shipbuilding, Tampa, Florida
Laid down: 15 March 1992
Completed: at Halter Marine Inc., Gulfport, Mississippi, in 1995
Launched: 28 August 1998
In service: 22 March 2001
Honors and
National Defense Service Medal
Status: in active service
General characteristics
Class and type: Impeccable-class ocean surveillance ship
Displacement: 5,368 tons
Length: 281 ft 5 in (85.78 m)
Beam: 95 ft 8 in (29.16 m)
Draft: 26 ft (7.9 m)
Propulsion: diesel-electric, two shafts, 5,000shp
Speed: 12 knots (22 km/h; 14 mph)
Complement: 25 civilian mariners, 25 military
Sensors and
processing systems:
SURTASS passive and active low frequency sonar arrays

USNS Impeccable (T-AGOS-23) is an Impeccable-class ocean surveillance ship acquired by the U.S. Navy in 2001 and assigned to Military Sealift Command's Special Missions Program.


Impeccable was built by American Shipbuilding, Tampa, Florida. The contract was awarded on 28 March 1991. The ship's keel was laid down on 15 March 1992, but the Tampa shipyards went bankrupt by November 1993.[1] On 3 December 1992, the General Accounting Office published a report that concluded that T-AGOS 24–27 should not be built.[2] Shortly afterwards the government decided to discontinue this class of ships, but the Impeccable was to be completed as the sole ship in its class. The hull was towed to Gulfport, Mississippi, in 1995 where it was finished by Halter Marine Inc.[3] She was launched on 28 August 1998 and was delivered to the Navy on 22 March 2001 which assigned her to the Military Sealift Command (MSC) Special Missions Program.[4]


The ship is a designated T-AGOS vessel built to tow a Surveillance Towed Array Sensor System. The ship's catamaran-type small waterplane area twin hull (SWATH) design prevents the vessel from rolling in heavy seas and gives additional deck space for storing the acoustic equipment.[5]


The mission of Impeccable is to directly support the Navy by using SURTASS passive and active low frequency sonar arrays to detect and track undersea threats.[citation needed]

Operational history[edit]

Low Frequency Active Sonar[edit]

  • The SURTASS Low Frequency Active Sonar system, onboard Impeccable, commenced sea trials in late February 2004. During the spring and summer of 2004, Impeccable conducted five training missions in the Philippine Sea and the northwest Pacific Ocean. All LFA sonar operations included the operation of the High Frequency / Marine Mammal Mitigation sonar and compliance with all mitigation requirements.[6]
  • Total operational days on board the Impeccable using the LFA array:
(15 August 2003 to 15 August 2004) 26.2 days with 63.0 hours of transmissions
(15 August 2004 to 15 August 2005) 9.4 days with 22.7 hours of transmissions
(15 August 2005 to 15 August 2006) 22.5 days with 39.4 hours of transmissions.[7]
  • The ship had five years of active and passive operations in the Western Pacific before the incident in the South China Sea.

South China Sea incidents[edit]

Two Chinese trawlers stop directly in front of the Impeccable, forcing the ship to conduct an emergency "all stop" in order to avoid collision.

On 5 March 2009, the Impeccable was in the South China Sea monitoring submarine activity[8] when it was approached by a People's Liberation Army Navy (PLAN) frigate, which crossed its bow at a range of approximately 100 yards without first making contact. This was followed less than two hours later by a Chinese Y-12 aircraft, conducting 11 flyovers of Impeccable at an altitude of 600 feet (180 m) and a range from 100–300 feet (30–90 m). The frigate then crossed Impeccable's bow again, this time at a range of approximately 400–500 yards.[9][10]

On 7 March, a Chinese intelligence ship contacted the Impeccable over bridge-to-bridge radio, calling her operations illegal and directing Impeccable to leave the area or "suffer the consequences."[11]

One Chinese crewmen waves a Chinese flag, while another uses a grappling hook to try to snag Impeccable's towed sonar array.

On 8 March 2009, the Impeccable was 75 miles south of Hainan, China, when it was shadowed by five Chinese ships: a Bureau of Maritime Fisheries Patrol Vessel, a State Oceanic Administration patrol vessel, a PLA Navy ocean surveillance ship, and two Chinese-flagged naval trawlers, which maneuvered close to the Impeccable, with two closing in to 50 feet (15 m), waving Chinese flags, and ordering the Impeccable from the area.[12][13] The Impeccable sprayed water at one of the nearest Chinese ships; the Chinese sailors stripped down to their underwear and their vessel closed in to within 25 feet of the American ship. Shortly after the incident, the Impeccable radioed the Chinese crews, informing them of its intentions to leave the area, and requesting a safe pass to travel. When it was trying to leave the area, the two Chinese trawlers dropped pieces of wood in the Impeccable's path and stopped directly in front of it, forcing it to do an emergency stop to avoid a collision.[14][15] Once the Impeccable got under way, the crew aboard one of the trawlers used a grappling hook to try to snag Impeccable's towed sonar array.[16]

The Hainan Submarine Base is on the island of Hainan. The nearby Paracel Islands are administered by China, but claimed by both Vietnam and Taiwan

The United States lodged formal protests following the incident, stating that under international law, the U.S. military can conduct activities "in waters beyond the territorial sea of another state without prior notification or consent" including in an exclusive economic zone of another country. "The unprofessional maneuvers by Chinese vessels violated the requirement under international law to operate with due regard for the rights and safety of other lawful users of the ocean."[15][17] China's Foreign Ministry responded that the Pentagon's complaints that five Chinese vessels had harassed the Impeccable were "totally inaccurate",[18][19] although this claim was disputed by several released reports, which all state that the Impeccable was interfered with numerous times, both while operating in the area and when attempting to leave.[20][21][22]

On 12 March 2009, U.S. President Barack Obama gave the go-ahead to send the guided missile destroyer USS Chung-Hoon to the South China Sea to protect the Impeccable while operating in that area.[23][24][25]

Hans M. Kristensen of the Federation of American Scientists has suggested that the incident may be related to the classified Type 093 submarine that the Chinese navy had recently deployed in the area.[26]

Views on the legality of US and Chinese actions during these incidents[edit]

China and the United States both maintain the rightfulness of their actions based on competing interpretations of the United Nations Convention on the Law of the Sea.

The United States maintains that the Convention, which it has signed, but not yet ratified, authorizes activities such as those undertaken by Impeccable.[18][27][28] Several legal experts also state that there is no legal foundation for China's claim that it can prevent foreign naval vessels from operating within its Exclusive Economic Zone. For example, Raul Pedrozo, writing in the Chinese Journal of International Law, concludes that "all nations may legitimately engage in military activities in foreign exclusive economic zones, without prior notice to, or consent of, the coastal State concerned."[29][30] On the contrary, Chinese officials assert that the operations are illegal. Rear Admiral Wang Dengping, political commissar of the Armament Department of the Chinese Navy, condemned the Impeccable's activities, stating that "Innocent passage by naval vessels from other countries in the Territorial waters in the Special Economic Zone is acceptable, but not allowed otherwise"[31] under the Convention. Chinese actions were further defended by Professor Ji Guoxing of Shanghai Jiao Tong University who, writing in China Security, maintained that under the Convention, navigation rights in coastal countries' exclusive economic zones are "subject to the resource-related and environment-related laws and regulations of the coastal state," and China could exclude the Impeccable on this basis. Ji further asserted that the Convention's prohibition against gathering military intelligence in another country's territorial waters should be interpreted to also prohibit intelligence gathering in coastal countries' exclusive economic zones.[32]

2015 rescue at sea[edit]

On July 19, 2015 while en route for a scheduled port visit to Subic Bay, USNS Impeccable (T-AGOS 23) rescued 11 fishermen. Impeccable sailors spotted personnel on a partially submerged ship and noted debris in the water. "They [Impeccable crew] initially spotted only eight people on the partially submerged vessel," said Lt. Cory Hilgart, the theater anti-submarine watch officer at Commander, Task Force 74. "They then realized that it was actually 11 and made the call to commence the rescue effort." The Impeccable's master immediately deemed assistance was required and began preparations to deploy their rigid hull inflatable boat (RHIB) to rescue the personnel. "This was a team effort with civilian mariners, SECDET [security detachment], MILDET [military detachment] and Lockheed Martin working together to achieve an efficient rescue of all 11 fishermen," said Robert Wiechert, Master of the Impeccable. The RHIB made three trips to the distressed vessel and recovered all eleven individuals. "One of the crew members spoke English," said Hilgart. "He told the Impeccable crew that they were fishermen from the Subic Bay region. He confirmed that there were only 11 on board." Once the mariners were brought aboard Impeccable, they were examined by medical personnel and given food and water. No serious injuries or illnesses were reported. Shortly after Impeccable arrived in port in Subic Bay, July 20, the mariners were turned over to the Philippine Coast Guard.[33][34]

Honors and awards[edit]

Impeccable personnel are qualified for the following medals:

See also[edit]


  1. ^ "American Ship Seeks Bankruptcy Protection". The New York Times. 5 November 1993. Retrieved 27 May 2010.
  2. ^ "Navy Continues to Build Ships Designed for Soviet Threat". Government Accountability Office. 3 December 1992. Retrieved 16 February 2019.
  3. ^ "USNS Impeccable (T-AGOS 23)". Naval Vessel Register. United States Navy. 21 October 2004. Retrieved 11 March 2009.
  4. ^ "Ship Inventory – USNS Impeccable (T-AGOS 23) – Ocean Surveillance Ship". Military Sealift Command. 5 December 2001. Archived from the original on 12 March 2009. Retrieved 16 February 2019.
  5. ^ "T-AGOS-23 Impeccable". Retrieved 16 February 2019.
  6. ^ "Taking Marine Mammals Incidental to Navy Operations of Surveillance Towed Array Sensor System Low Frequency Active Sonar". Federal Register. 70 (164): 49914–49915. 25 August 2005. Retrieved 16 February 2019.
  7. ^ Department of the Navy, Chief of Naval Operations (January 2007). "Final Comprehensive Report for the Operation of the Surveillance Towed Array Sensor System Low Frequency Active (SURTASS LFA)" (PDF). NOAA. Archived from the original (PDF) on 28 January 2017. Retrieved 16 February 2019.
  8. ^ "Officials: Ship in China spat was hunting subs". MSNBC. 10 March 2009. Archived from the original on 12 March 2009. Retrieved 16 February 2019.
  9. ^ "USNS Impeccable: Chinese Vessels Harass US Navy Ship". Blue Star Chronicles. 9 March 2009. Archived from the original on 12 March 2009. Retrieved 16 February 2019.
  10. ^ "Pentagon says Chinese vessels harassed U.S. ship". CNN. 9 March 2009. Retrieved 16 February 2019.
  11. ^ Capaccio, Tony (9 March 2009). "Chinese Vessels Harass U.S. Navy Ship, Pentagon Says". Bloomberg News. Archived from the original on 24 October 2012. Retrieved 16 February 2019.
  12. ^ "Pentagon: Chinese vessels harassed unarmed ship". Associated Press. 9 March 2009. Archived from the original on 12 March 2009. Retrieved 16 February 2019.
  13. ^ Miller, James (10 March 2009). "USNS Impeccable". Ocean Engineering Blog. Archived from the original on 12 March 2009. Retrieved 16 February 2019.
  14. ^ "U.S. protests harassing of Navy ship by Chinese". NBC News. 9 March 2009. Retrieved 16 February 2019.
  15. ^ a b Tyson, Ann Scott (10 March 2009). "U.S. Protests Chinese Shadowing in International Waters". The Washington Post. Retrieved 16 February 2019.
  16. ^ Miklaszewski, Jim; Kube, Courtney (9 March 2009). "Close call off South China Sea". MSNBC. Archived from the original on 11 March 2009. Retrieved 16 February 2019.
  17. ^ Morgan, David (9 March 2009). "U.S. says Chinese vessels harassed Navy ship". Reuters. Retrieved 16 February 2019.
  18. ^ a b "China hits out at US on navy row". BBC News. 10 March 2009. Retrieved 16 February 2019.
  19. ^ "China says U.S. naval ship breaks int'l, Chinese law". Xinhua News Agency. 10 March 2009. Archived from the original on 13 March 2009. Retrieved 16 February 2019.
  20. ^ Gearan, Anne (10 March 2009). "Officials: US ship in China spat was hunting subs". Yahoo! News. Archived from the original on 18 March 2009. Retrieved 16 February 2019.
  21. ^ Pilkington, Ed (10 March 2009). "Stand-off shows Chinese navy's secret tactics". The Guardian. London. Retrieved 27 May 2010.
  22. ^ Santo, Michael (9 March 2009). "Spy Ship USNS Impeccable Harassed by Chinese Ships: Report". HULIQ. Retrieved 16 February 2019.
  23. ^ Reid, Tim (14 March 2009). "US warships head for South China Sea after standoff". The Times. London. Archived from the original on 29 April 2011. Retrieved 27 May 2010.
  24. ^ Tyson, Ann Scott (13 March 2009). "Navy Sends Destroyer to Protect Surveillance Ship After Incident in South China Sea". The Washington Post. Retrieved 27 May 2010.
  25. ^ "Obama Calls for Improved Military Dialogue Between U.S. and China, After Naval Confrontation". Fox News. 12 March 2009. Archived from the original on 15 March 2009.
  26. ^ Kristensen, Hans M. (9 March 2009). "US-Chinese Anti-Submarine Cat and Mouse Game in South China Sea". Federation of American Scientists. Retrieved 16 February 2019.
  27. ^ "US and China Face Off in South China Sea". Sky News. 9 March 2009. Archived from the original on 12 March 2009. Retrieved 10 March 2009.
  28. ^ "Chinese ships 'harass' US vessel". BBC News. 9 March 2009. Retrieved 16 February 2019.
  29. ^ Johnson, Tim (10 March 2009). "Why did China choose now to surround a U.S. warship?". McClatchyDC. Archived from the original on 13 March 2009. Retrieved 11 March 2009.
  30. ^ Pedrozo, Raul (Pete) (1 March 2010). "Preserving Navigational Rights and Freedoms: The Right to Conduct Military Activities in China's Exclusive Economic Zone". Chinese Journal of International Law. 9 (1): 9–29. Retrieved 16 February 2019 – via SSRN.
  31. ^ "Navy lawmaker: Violation of China's sovereignty not allowed". Xinhua News Agency. 10 March 2009. Archived from the original on 7 November 2012. Retrieved 7 December 2010.
  32. ^ Ji Guoxing (Spring 2009). "The Legality of the 'Impeccable Incident'" (PDF). China Security. 5 (2). Archived from the original (PDF) on 27 March 2012. Retrieved 14 September 2011.
  33. ^ Reynolds, Brian G. (20 July 2015). "USNS Impeccable Rescues Distressed Fishermen". U.S. Navy Submarine Group 7 Public Affairs. Retrieved 16 February 2019.
  34. ^ "USNS Impeccable crew rescues Filipino fishermen". Stars and Stripes. 20 July 2015. Retrieved 16 February 2019.

This article includes information collected from the Naval Vessel Register, which, as a U.S. government publication, is in the public domain. The entry can be found here.

External links[edit]