DULLES, Va.Dec. 7, 2006--Orbital Sciences Corporation (NYSE: ORB) announced today that it commenced a tender offer for cash to purchase any and all of the $126,425,000 outstanding aggregate principal amount of its 9% Senior Notes due 2011. In connection with the tender offer, Orbital is soliciting consents to effect certain proposed amendments to the indenture governing the 9% Senior Notes. The tender offer and consent solicitation are being made pursuant to an Offer to Purchase and Consent Solicitation Statement dated December 7, 2006, and a related Consent and Letter of Transmittal, which more fully set forth the terms and conditions of the tender offer and consent solicitation.

As described in the Offer to Purchase and Consent Solicitation Statement, the total consideration to be paid for each $1,000 principal amount of 9% Senior Notes validly tendered and accepted for purchase will be determined using a yield equal to a fixed spread of 50 basis points plus the bid-side yield to maturity of the 3.625% U.S. Treasury Note due June 30, 2007. The pricing of the total consideration is expected to occur at 2:00 p.m., New York City time, on December 20, 2006 (such date subject to adjustment). The total consideration includes a consent payment of $20 per $1,000 principal amount of 9% Senior Notes payable only to holders who tender (and do not validly withdraw) their 9% Senior Notes and validly deliver (and do not validly revoke) their consents prior to the consent payment deadline. Holders who tender (and do not validly withdraw) their 9% Senior Notes after the consent payment deadline but before the expiration date will be eligible to receive the tender offer consideration, which is the total consideration minus the consent payment. Holders who tender (and do not validly withdraw) their 9% Senior Notes will receive the accrued and unpaid interest on such 9% Senior Notes to, but not including, the applicable payment date in connection with the tender offer. The consent payment deadline is scheduled to be 5:00 p.m., New York City time, on December 20, 2006, unless terminated or extended.

The tender offer is scheduled to expire at midnight, New York City time, on January 5, 2007, unless terminated or extended.

The proposed amendments to the indenture governing the 9% Senior Notes would eliminate most of the indenture's principal restrictive covenants and certain events of default and related provisions and would significantly amend certain other provisions contained in the indenture. Adoption of the proposed amendments requires the consent of the holders of at least a majority of the aggregate principal amount of the 9% Senior Notes outstanding. Holders who tender their 9% Senior Notes will be required to consent to the proposed amendments and holders may not deliver consents to the proposed amendments without tendering their 9% Senior Notes in the tender offer. Tendered 9% Senior Notes may be withdrawn and consents may be revoked at any time prior to the consent payment deadline, but not thereafter.

The tender offer is conditioned upon, among other things, (a) the receipt of tendered 9% Senior Notes from the holders of at least a majority of the aggregate principal amount of the 9% Senior Notes outstanding and (b) the receipt of consents to the proposed amendments from the holders of at least a majority of the aggregate principal amount of the 9% Senior Notes outstanding, and (c) the company having sufficient funds to purchase the 9% Senior Notes pursuant to the tender offer and to pay the tender offer consideration and consent payment, if any.

Wachovia Securities is acting as exclusive dealer manager and solicitation agent for the Tender Offer and the Consent Solicitation. The information agent and tender agent for the tender offer is D.F. King & Co., Inc. Questions regarding the tender offer and consent solicitation may be directed to Wachovia Securities's Liability Management Group, telephone number 866-309-6316 (toll free) and 704-715-8341 (call collect). Requests for copies of the Offer to Purchase and Consent Solicitation Statement and related documents may be directed to D.F. King & Co., Inc., telephone number 800-758-5378 (toll free) and 212-269-5550 (call collect).

This announcement is not an offer to purchase, a solicitation of an offer to sell, or a solicitation of consents with respect to the 9% Senior Notes nor is this announcement an offer to sell or solicitation of an offer to purchase new securities. The tender offer and consent solicitation are made solely by means of the Offer to Purchase and Consent Solicitation Statement and the related Consent and Letter of Transmittal.

About Orbital

Orbital develops and manufactures small rockets and space systems for commercial, military and civil government customers. Orbital's primary products are satellites and launch vehicles, including low-orbit, geosynchronous-orbit and planetary spacecraft for communications, remote sensing, scientific and defense missions; ground- and air-launched rockets that deliver satellites into orbit; and missile defense systems that are used as interceptor and target vehicles. Orbital also offers space-related technical services to government agencies and develops and builds satellite-based transportation management systems for public transit agencies and private vehicle fleet operators.

More information about Orbital can be found at http://www.orbital.com

Safe Harbor Statement

Certain statements in this press release may be forward-looking in nature or "forward-looking statements" as defined in the Private Securities Litigation Reform Act of 1995. Such forward-looking statements are subject to risks, trends and uncertainties that could cause the actual results or performance of the company to be materially different from the forward-looking statement. Uncertainty surrounding factors such as continued government support and funding for key space and defense programs, product performance and market acceptance of products and technologies, the outcome of the government investigation, as well as other risk factors and business considerations described in the company's SEC filings, including its annual report on Form 10-K/A, could impact Orbital's actual financial and operational results. Orbital assumes no obligation for updating the information contained in this press release.


    CONTACT: Orbital Sciences Corporation
             Public and Investor Relations
             Barron Beneski, 703-406-5528
             Beneski.barron@orbital.com

    SOURCE: Orbital Sciences Corporation